Showing posts with label allopregnanolone. Show all posts
Showing posts with label allopregnanolone. Show all posts

Tuesday 6 November 2018

When is an SSRI not an SSRI? Low dose SSRIs as Selective Brain Steroidogenic Stimulants (SBSSs) via Allopregnanolone modifying GABAa receptors and neonatal KCC2 expression

Today’s post might seem to have a very complicated tittle, but to regular readers it is really just another take on what we have seen time and time again.
Today we see how another steroid imbalance in autism – low levels of allopregnenolone in this case – affects the neurotransmitter GABA and indeed the chloride transporter KCC2.

Putting Prozac/Zoloft to a better use?

I did report previously on a trial in adults with autism where pregnenolone was used.

Recall that disturbed hormonal homeostasis is a key feature of autism. What matters is the level of each hormone inside the brain (i.e. centrally), not in your blood. The only way to get a reliable idea of what is going on would be to take a sample of spinal fluid.

Today we look at boosting allopregnenolone not with a steroid hormone, but with a 1/10th dose of Prozac (Fluoxetine) or indeed Zoloft (Sertraline). Prozac is a selective serotonin reuptake inhibitor (SSRI) when given at the usual dose of 20-80mg, but at 2.5mg it does not function as an SSRI.
At regular doses selective serotonin reuptake inhibitors (SSRI) drugs like Prozac are well known to cause problems, as do benzodiazepines like Clonazepam.
Thanks to Professor Catterall we saw in earlier posts how tiny doses of Clonazepam have an effect on one particular sub-unit of GABAA receptors. By fine tuning the response of this receptor we saw how a cognitive improvement can be achieved, in some people. The dose is so low there appear to be no long term side effects. At least one other professor of medicine, I am in contact with, has been treating his son with autism with low dose clonazepam for years.
Many adults and children with autism are prescribed Prozac for anxiety. Even Temple Grandin has said she takes Prozac.
At low, non-serotonergic doses, some drugs like Prozac show a different mode of action, they potently, positively, and allosterically modulate GABA action at GABAA receptors. These drugs achieve this by increasing the amount of the steroid hormone allopregnanolone.
Neurosteroid biosynthesis down‐regulation and changes in GABAA receptor subunit composition are a feature of several neurological conditions, including some autism.
Stimulating allopregnenalone biosynthesis will have multiple effects including on TSPO and endocannabinoid receptors.

Brain principal glutamatergic neurons synthesize 3α-hydroxy-5α-pregnan-20-one (Allo), a neurosteroid that potently, positively, and allosterically modulates GABA action at GABAA receptors. Cerebrospinal fluid (CSF) Allo levels are decreased in patients with posttraumatic stress disorder (PTSD) and major depression. This decrease is corrected by fluoxetine in doses that improve depressive symptoms. Emotional-like behavioral dysfunctions (aggression, fear, and anxiety) associated with a decrease of cortico-limbic Allo content can be induced in mice by social isolation. In socially isolated mice, fluoxetine and analogs stereospecifically normalize the decrease of Allo biosynthesis and improve behavioral dysfunctions by a mechanism independent from 5-HT reuptake inhibition. Thus, fluoxetine and related congeners facilitate GABAA receptor neurotransmission and effectively ameliorate emotional and anxiety disorders and depression by acting as selective brain steroidogenic stimulants (SBSSs).                               
When the results of these in vitro studies are compared to those of our in vivo studies, it becomes evident that in mice the doses of fluoxetine and norfluoxetine that cause a rapid increase in brain Allo levels do not exceed brain concentrations in the low nanomolar range, whereas the fluoxetine concentrations that directly activate 3a-HSD in vitro are in the micromolar range. Moreover, the high potency and stereospecificity of fluoxetine and norfluoxetine in decreasing aggressive behavior and normalizing brain Allo content during social isolation (see Table 1, and Figure 3) support the notion that these compounds facilitate the action of 5a-R type I or 3a-HSD by an unidentified indirect mechanism, which is most probably perturbed by protracted social isolation.

Thus, these drugs, which were originally termed ‘SSRI’ antidepressants, may be beneficial in psychiatric disorders because in doses that are inactive on 5-HT reuptake mechanisms, they increase the bioavailability of neuroactive GABAergic steroids. On the basis of these considerations, we now propose that the term ‘SSRIs’ should be changed to the more appropriate term ‘selective brain steroidogenic stimulants’ (SBSSs), which more accurately defines the pharmacological mechanisms expressed by fluoxetine and its congeners.


The pharmacology of the S stereoisomers of fluoxetine and norfluoxetine appears to be prototypic for molecules that possess specific neurosteroidogenic activity. The doses of S-fluoxetine and S-norfluoxetine required to normalize brain Allo content downregulation, pentobarbital action, aggressiveness, and anxiety in socially isolated mice are between 10-fold to 50-fold lower than those required to induce SSRI activity. However, the precise mechanisms of action by which S-fluoxetine and S-norfluoxetine increase neurosteroids remain to be investigated.

Derivatives of S-fluoxetine and S-norfluoxetine, acting with high potency and specificity on brain neurosteroid expression at doses devoid of significant action on brain 5-HT reuptake mechanisms, may represent a new class of pharmacological tools important for the management of anxiety, related mood disorders, dysphoria, fear, and impulsive aggression.

On the basis of these data, new drugs devoid of SSRI activity but that are potent neurosteroidogenic agents should be developed for the treatment of psychiatric disorders that result from the downregulation of neurosteroid expression, including major depression, and in the prevention of PTSD.

France often gets very negative comments about how it treats people with autism, but in the case studies below it looks like some innovative work is going on in some of their day hospitals, where boys and girls with severe autism are sent to pass their time. 

The system in England has recently been highlighted as being pretty appalling, where over 2,000 people with autism are currently detained in Assessment and Treatment Units (ATUs), privately run secure residential "hospitals", at great cost paid for by the State. Those inside might enter with the approval of their family to stay for 3 weeks for respite care, but end up being detained for 3 years, or even longer. The State assumes their guardianship and the individual and parents are powerless. The individuals are kept in prison-like conditions and not surprisingly get worse not better, the worse they get, the harder it is ever to be released. Hard to believe this is still happening.  If you live in England, best not to hand your child over to the State. Someone has even written a book about escaping from such a unit. This is no better than the old State Hospitals in the US, that finally were closed down in the 1970s, that warehoused mentally disabled people, until their premature death.

Autism Spectrum Disorder (ASD) is defined by the copresence of two core symptoms: alteration in social communication and repetitive behaviors and/or restricted interests. In ASD children and adults, irritability, self-injurious behavior (SIB), and Attention Deficit and Hyperactivity Disorders- (ADHD-) like symptoms are regularly observed. In these situations, pharmacological treatments are sometimes used. Selective Serotonin Reuptake Inhibitors- (SSRI-) based treatments have been the subject of several publications: case reports and controlled studies, both of which demonstrate efficacy on the symptoms mentioned above, even if no consensus has been reached concerning their usage. In this article four clinical cases of children diagnosed with ASD and who also present ADHD-like symptoms and/or SIB and/or other heteroaggressive behaviors or irritability and impulsivity treated with low doses of fluoxetine are presented.
Case 1 
An 8-year-old girl (19 kg) had an ASD diagnosis according to the DSM-5 and ADI-R criteria based on information provided by parents. She also had significant mental retardation, with severe SIB (banging her head against objects and biting her hands), forcing her entourage to maintain a daily and permanent physical restraint. She spends most of her time in a day hospital. She received the following pharmacological treatment: risperidone 2 mg/d and cyamemazine 80 mg/d without modifications to her SIB and at the price of a major slowing down and a manifestation of a tendency toward blunting. The CGI severity of illness score was at five (markedly ill). We decreased and stopped risperidone and started valproic acid. After four weeks of valproic acid 400 mg/d in combination with cyamemazine (60 mg/day), SIBs did not improve. Then, we added fluoxetine 2.5 mg/d and increased it after one week to 5 mg/d and to 10 mg/d in the third week. After one week, the CGI improvement scale (CGI-I) was at two; after three weeks, it lowered to 1 (very much improved). We also observed a significant decrease in anxiety as well as the disappearance of SIB (disappearance of the behavior consisting of the banging and rubbing her head against objects). However, it should be noted that the entourage kept the bandages on her hands because she continued to bite them, even if she did it with less intensity than before. There were no side effects. After three months of fluoxetine, her clinical state remains stable.

Case 2 
A 12-year-old boy (70 kg), with DSM-5 criteria for an ASD and ADI-R confirming this diagnosis, exhibited extreme irritability, violence, and impulsiveness as well as SIB (he had thrown seven television sets out of the window). The CGI severity illness scoring was at six (severely ill). In the day hospital where he spent most of his time, it was difficult for staff to manage his impulsivity and unpredictability. His treatment included risperidone 4 mg/d as well as loxapine 80 mg/d. Despite this pharmacological treatment, episodes of aggression and SIBs continued. This treatment induced a significant weight gain (8 kg in 5 months). Treatment with fluoxetine 2.5mg/d was introduced and increased to5mg/d after one week and to 10 mg/d at the beginning of the third week. After one week, there was a CGI-I score of three, which decreased to two after two weeks of treatment and to one after three weeks. Such a positive clinical response allowed for a reduction in risperidone to 2mg/d and in loxapine to 60 mg/d. The treatment was tolerated well by the patient, and he began to lose weight (4 kg). After two months off luoxetine, his clinical state remains stable.

Case 3
 A 6-year-old male child (30 kg) with DSM-5 criteria and ADI-R for an ASD exhibited problems of SIB and repetitive behaviors (washing his hands for more than 30 minutes at least two to three times per day), severe irritability, frequent crying, social withdrawal, and inappropriate speech. Treatment with risperidone 2mg/d had improved irritability and partially the SIB, but it had also produced significant weight gain (four kg in three months). A decrease in the risperidone dosage seemed necessary. Treatment with fluoxetine2.5mg/d was begun, which quickly led to a reduction in inappropriate behavior (for example, impulsive crawling on the ground in the classroom). After one week, the CGI-I scoring was at two. The dosage was gradually increased to 5 mg/d the second week and to 7.5mg/d the third week. The repetitive behaviors gradually subsided. After three weeks the CGI-I score was at one, and it remained stable for nine weeks. The risperidone dosage could be decreased to 0,5 mg/day and the patient’s weight remained the same.
Case 4 
A 12-year-old boy (62kg) withDSM-5 and ADI-R criteria for a severe case of ASD, including severe ADHD-like symptoms, often required physical restraint and did not improve despite a long-term treatment of risperidone 3 mg/d as well as melaton in 4mg at bedtime. The CGI severity illness scoring was at 6 (severely ill). The behavioral pattern included irritability, marked agitation, crying, severe hyperactivity, and other behaviors typical of this disorder. He was also anxious, rendering the situation at his day hospital where he spent most of his time all the more difficult. A prescription of fluoxetine 2.5mg/d was initiated with an immediate and complete improvement of ADHD-like symptoms:CGI-I at one week of treatment was at a one, making this case the most remarkable of the four presented here. Treatment with fluoxetine was continued with a dosage increase up to 5 mg/d to allow for a decrease in the risperidone dose to 1 mg/d. CGI-I score remained stable at one for the duration of the nine weeks.

Our reader Mira, whose son has FXS, recently referred to Dr Hagerman’s trial of low dose Sertaline/Zoloft in Fragile X. GABAA malfunction appears to be a feature of Fragile X, but it is not necessarily the identical malfunction to those with idiopathic autism who respond to bumetanide.


Observational studies and anecdotal reports suggest sertraline, a selective serotonin reuptake inhibitor (SSRI), may improve language development in young children with fragile X syndrome (FXS). We evaluated the efficacy of six months of treatment with low-dose sertraline in a randomized, double-blind, placebo-controlled trial in 52 children with FXS ages 2–6 years.


Eighty-one subjects were screened for eligibility and 57 were randomized to sertraline (27) or placebo (30). Two subjects from the sertraline arm and three from the placebo arm discontinued. Intent-to-treat analysis showed no difference from placebo on the primary outcomes: the Mullen Scales of Early Learning (MSEL) expressive language age equivalent and Clinical Global Impression-Improvement (CGI-I). However, analyses of secondary measures showed significant improvements, particularly in motor and visual perceptual abilities and social participation. Sertraline was well tolerated, with no difference in side effects between sertraline and placebo groups. No serious adverse events occurred.


This randomized controlled trial of six-months of sertraline treatment showed no primary benefit with respect to early expressive language development and global clinical improvement. However, in secondary, exploratory analyses there were significant improvements seen on motor and visual perceptual subtests, the Cognitive T score sum on the MSEL, and on one measure of Social Participation on the Sensory Processing Measure–Preschool. Further, post hoc analysis found significant improvement in early expressive language development as measured by the MSEL among children with ASD on sertraline. Treatment appears safe for this 6-month period in young children with FXS, but we do not know the long-term side effects of this treatment. These results warrant further studies of sertraline in young children with FXS using refined outcome measures, as well as longer term follow-up studies to address long-term side effects of low-dose sertraline in early childhood.

Neurosteroid biosynthesis down‐regulation and changes in GABAA receptor subunit composition: a biomarker axis in stress‐induced cognitive and emotional impairment

By rapidly modulating neuronal excitability, neurosteroids regulate physiological processes, such as responses to stress and development. Excessive stress affects their biosynthesis and causes an imbalance in cognition and emotions. The progesterone derivative, allopregnanolone (Allo) enhances extrasynaptic and postsynaptic inhibition by directly binding at GABAA receptors, and thus, positively and allosterically modulates the function of GABA. Allo levels are decreased in stress-induced psychiatric disorders, including depression and post-traumatic stress disorder (PTSD), and elevating Allo levels may be a valid therapeutic approach to counteract behavioural dysfunction. While benzodiazepines are inefficient, selective serotonin reuptake inhibitors (SSRIs) represent the first choice treatment for depression and PTSD. Their mechanisms to improve behaviour in preclinical studies include neurosteroidogenic effects at low non-serotonergic doses. Unfortunately, half of PTSD and depressed patients are resistant to current prescribed 'high' dosage of these drugs that engage serotonergic mechanisms. Unveiling novel biomarkers to develop more efficient treatment strategies is in high demand. Stress-induced down-regulation of neurosteroid biosynthesis and changes in GABAA receptor subunit expression offer a putative biomarker axis to develop new PTSD treatments. The advantage of stimulating Allo biosynthesis relies on the variety of neurosteroidogenic receptors to be targeted, including TSPO and endocannabinoid receptors. Furthermore, stress favours a GABAA receptor subunit composition with higher sensitivity for Allo. The use of synthetic analogues of Allo is a valuable alternative. Pregnenolone or drugs that stimulate its levels increase Allo but also sulphated steroids, including pregnanolone sulphate which, by inhibiting NMDA tonic neurotransmission, provides neuroprotection and cognitive benefits. In this review, we describe current knowledge on the effects of stress on neurosteroid biosynthesis and GABAA receptor neurotransmission and summarize available pharmacological strategies that by enhancing neurosteroidogenesis are relevant for the treatment of SSRI-resistant patients. Linked Articles This article is part of a themed section on Pharmacology of Cognition: a Panacea for Neuropsychiatric Disease? To view the other articles in this section visit

Too little allopregnanalone can induce autism.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with core symptoms of social impairments and restrictive repetitive behaviors. Recent evidence has implicated a dysfunction in the GABAergic system in the pathophysiology of ASD. We investigated the role of endogenous allopregnanolone (ALLO), a neurosteroidal positive allosteric modulator of GABAA receptors, in the regulation of ASD-like behavior in male mice using SKF105111 (SKF), an inhibitor of type I and type II 5α-reductase, a rate-limiting enzyme of ALLO biosynthesis. SKF impaired sociability-related performance, as analyzed by three different tests; i.e., the 3-chamber test and social interaction in the open field and resident-intruder tests, without affecting olfactory function elucidated by the buried food test. SKF also induced repetitive grooming behavior without affecting anxiety-like behavior. SKF had no effect on short-term spatial working memory or long-term fear memory, but enhanced latent learning ability in male mice. SKF-induced ASD-like behavior in male mice was abolished by the systemic administration of ALLO (1mg/kg, i.p.) and methylphenidate (MPH: 2.5mg/kg, i.p.), a dopamine transporter inhibitor. The effects of SKF on brain ALLO contents in male mice were reversed by ALLO, but not MPH. On the other hand, SKF failed to induce ASD-like behavior or a decline in brain ALLO contents in female mice. These results suggest that ALLO regulates episodes of ASD-like behavior by positively modulating the function of GABAA receptors linked to the dopaminergic system. Moreover, a sex-dependently induced decrease in brain ALLO contents may provide an animal model to study the main features of ASD.

Some steroids, whose levels are raised in autism (allopregnanolone, androsterone, pregnenolone, dehydroepiandrosterone and their sulfate conjugates) are neuroactive and modulate GABA, glutamate, and opioid neurotransmission, affecting brain development and functioning. These steroids may contribute to autism pathobiology and symptoms such as elevated anxiety, sleep disturbances, sensory deficits, and stereotypies among others.

Tuning the Brain
I did write a post a while back to show the effect of tuning GABAa receptors.

The effect of allopregnanolone of KCC2 expression and hence the level of chloride within neurons.

Neonatal allopregnanolone or finasteride administration modifies hippocampal K(+) Cl(-) co-transporter expression during early development in male rats.


The maintenance of levels of endogenous neurosteroids (NS) across early postnatal development of the brain, particularly to the hippocampus, is crucial for their maturation. Allopregnanolone (Allop) is a NS that exerts its effect mainly through the modulation of the GABAA receptor (GABAAR). During early development, GABA, acting through GABAAR, that predominantly produces depolarization shifts to hyperpolarization in mature neurons, around the second postnatal week in rats. Several factors contribute to this change including the progressive increase of the neuron-specific K(+)/Cl(-) co-transporter 2 (KCC2) (a chloride exporter) levels. Thus, we aimed to analyze whether a different profile of NS levels during development is critical and can alter this natural progression of KCC2 stages. We administrated sustained Allop (20mg/kg) or Finasteride (5α-reductase inhibitor, 50mg/kg) from the 5th postnatal day (PD5) to PD9 and assessed changes in the hippocampal expression of KCC2 at transcript and protein levels as well as its active phosphorylated state in male rats. Taken together data indicated that manipulation of NS levels during early development influence KCC2 levels and point out the importance of neonatal NS levels for the hippocampal development.                                                                                                                           

Add very low dose Prozac to the long list of possible SIB therapies, more practical than electroconvulsive therapy (ECT), that is for sure!

This post was long waiting in my “to-complete” pile. I thought it would be a short one, but it kept growing.  It does draw together several interesting issues and shows there is a pattern developing in all these blog posts.
The majority of psychiatric drugs have such severe drawbacks that the great majority of children are better off without them.  However, there are many existing drugs that have little known neurological effects that can be highly beneficial and are known to be safe to use long term.
Psychiatric drugs that can be repurposed at lower dosages for different purposes may indeed be free of the major drawbacks encountered at higher doses.
It looks like humans with Fragile X Syndrome (FXS) are leading the way with low dose SSRI therapy to modulate GABA.  It would seem highly plausible that other idiopathic autism might also benefit and the French case studies in this post are examples of those who did benefit.
I think this is another example of fine-tuning the brain to optimize its functioning. It probably will not produce miracles, but the science shows that allopregnenalone can be tuned to vary mood in humans.  Low levels of allopregnenalone can produce autistic-like behaviours in mouse models.
The effect of allopregnenalone on KCC2 expression may only be present in tiny babies, if it continues into childhood that would be another reason to consider it as a target for modulation.  If that were the case, then Finasteride the cheap generic drug for prostate enlargement, should be investigated.
As is always the case in autism, both extremes are likely to exist; some people will likely benefit from low dose SSRIs but it will make some others worse (anxiety, SIB etc). If you start with elevated allopregnenalone, you would want less, not more.
Repurposing existing drugs has huge unrealized potential.
The OTC antihistamine Clemastine, which I highlighted in an earlier post as being a Positive Allosteric Modulator (PAM) of P2X7, and so helps remyelination, is yet another example of repurposing a safe drug.  Reportedly, it has this effect even below the regular dosage for allergy; at the high dosage usage in MS trials it will send you to sleep and risk some other side effects. As MS is not a singular condition, it seems that some people respond much more so than others. It also seems to have a benefit is some psychiatric disorders; not bad for a cheap OTC antihistamine.

Thursday 19 February 2015

Why Low Doses can work differently, or “Biphasic, U-shaped actions at the GABAa receptor”

This post does get a little complicated, so here is a summary.

Key points

·        High doses of oral Pregnenolone are shown to help Schizophrenia, particularly in females.  (these are all adults)

·        High dose oral Pregnenolone has also been shown to help adults with autism.

·        Low doses of transdermal progesterone (and likely Pregnenolone), anecdotally, reduce anxiety in Asperger’s and ADHD

·        Unusual levels of various hormones are a hallmark of autism, this can directly affect neurotransmitters like GABA

·        Hormones are produced in the brain as well as elsewhere in the body and so supplementing them may have unintended side effects.  Some hormones do not cross the blood brain barrier.

·        Side effects should be less likely after puberty, so research is done on adults

·        Some people regularly give very young children hormones, like melatonin

·        It may be possible to get the benefit of the hormones affecting GABAA at low doses

·        Changes in certain hormone levels actually change the structure (and hence the effect) of the GABAA receptor

·        Modulating the GABAA receptor via the neurosteroid site then changes how the Benzo site of the same receptor responds to modulation (hence changes the effect, and side effects of Benzodiazepines)

Today’s post has a very odd tittle.

It will explain some of the odd things that we have been seeing in seizure drugs having potent effects at tiny doses.  It really is a case where “less is more”.

We will see that modulating the GABAA receptor using the neurosteroid binding site (not the usual Benzo site) has potential for many neurological conditions.  There are some interesting interventions possible today and some are OTC.  We will also see that the structure of the GABAA receptor is itself dynamic and some drugs affecting it are actually changing it.

This is all very relevant because it appears that GABAA dysfunction is at the very core of the common autism variants and a key factor in schizophrenia.
I did say in a recent post that  GABAA receptor is rather complicated and best left to Professors Sigel and Catterall and their mice, but then I came across the explanation myself.  As usual, the answer is there in the science, you just have to know where to look for it; or just stumble upon it.

It also appears that the recent autism trial at Stanford of pregnenolone, may have left untold part of the story.  They gave increasing high doses of pregnenolone, which is converted in the body into allopregnanolone, a positive allosteric modulator of GABAA receptors. 

At tiny doses, allopregnanolone stimulates GABAA, at higher doses it inhibits it and then at very high doses again it stimulates it.  So the precise dosage of Pregnenolone, or indeed progesterone, which also produces allopregnanolone, would be critical in achieving the desired modulation of GABA.  The Stanford researcher is a psychiatrist, by the way, not a biochemist; he did not investigate the effect of small doses.

There are a whole raft of similar studies in the works, trialing Pregnenolone in Schizophrenia, Bipolar, TBI and even Gulf War Illnesses.


As usual the most up-to-date source is Wikipedia:-


Allopregnanolone possesses a wide variety of effects, including, in no particular order, antidepressant, anxiolytic, stress-reducing, rewarding, prosocial, antiaggressive, prosexual, sedative, pro-sleep, cognitive and memory-impairing, analgesic, anesthetic, anticonvulsant, neuroprotective, and neurogenic effects.
Fluctuations in the levels of allopregnanolone and the other neurosteroids seem to play an important role in the pathophysiology of mood, anxiety, premenstrual syndrome, catamenial epilepsy, and various other neuropsychiatric conditions.
Increased levels of allopregnanolone can produce paradoxical effects, including negative mood, anxiety, irritability, and aggression. This appears to be because allopregnanolone possesses biphasic, U-shaped actions at the GABAA receptor – moderate level increases (in the range of 1.5–2 nM/L total allopregnanolone, which are approximately equivalent to luteal phase levels) inhibit the activity of the receptor, while lower and higher concentration increases stimulate it. This seems to be a common effect of many GABAA receptor positive allosteric modulators. In accordance, acute administration of low doses of micronized progesterone (which reliably elevates allopregnanolone levels), have been found to have negative effects on mood, while higher doses have a neutral effect.

Possible Explanations for the Paradoxical Effect of GABA-Steroids
In this section, possible mechanisms of the biphasic response curve of allopregnanolone on behavioral parameters are discussed. The basic idea of so called paradoxical effect where neurosteroids show one type of effect at low concentrations and another type at high concentrations is that an enhanced GABAA-receptor activity may give an excitatory net effect in certain situations, instead of the usual inhibitory effect. The following hypotheses suggest several possible mechanisms how this can be achieved. In addition, there are no contradictions between the different hypothesis and they may very well act in parallel.

The Effect of Neurosteroids on the GABAA-Receptor
The GABAA-receptor can be modulated by a number of therapeutic agents, including benzodiazepines , barbiturates , anesthetics, ethanol , zinc , and neurosteroids . The effect of neurosteroids on the GABAA-receptor depends on the type of steroids (agonist or antagonist), the type of receptors (synaptic of extrasynaptic), the subunit compositions, and the intrinsic structure of the steroid. Recent studies indicate that the existence of at least two neurosteroid actions on the GABAA-receptor, namely an agonistic action and an antagonistic action by the sulfated and 3β-OH steroids. The agonistic action can further be divided into an allosteric enhancement of GABA-evoked Cl current and a direct activation of the GABAA-receptor.

It is puzzling why an increase in allopregnanolone during the menstrual cycle is related to development of negative mood as allopregnanolone should be anxiolytic agent like benzodiazepines. The answer depends on the fact that all GABAA-receptor agonists such as benzodiazepines, barbiturates, alcohol, and allopregnanolone have paradoxical anxiogenic effects in certain individuals. At low concentrations or doses they give severe adverse emotional reactions in a subset of individuals (3–6%) and moderate reactions in up to 20–30% of individuals. This paradoxical effect is induced by allopregnanolone  benzodiazepines , barbiturates , and ethanol . Symptoms induced by these GABAA-receptor active drugs are depressive mood, irritability, aggression, and other symptoms known to occur during the luteal phase in women with PMS/PMDD. A biphasic effect was also observed for medroxyprogesterone (MPA) and natural progesterone in postmenopausal women taking hormone therapy. These women felt worse on a lower dosage of MPA or progesterone than on a higher dosage or placebo.
Thus allopregnanolone seems to have a biphasic effect on mood with an inverted U-shaped relationship between concentration and effect. In postmenopausal women receiving progesterone, a biphasic relation between the negative mood symptoms and the plasma concentrations of allopregnanolone was observed. The negative mood increased with the elevating serum concentration of allopregnanolone up to the maximum concentration seen at the luteal phase. With further increase in allopregnanolone concentration there was a decrease in symptom severity  An inverted U-shaped relation between allopregnanolone dosage and irritability/aggression has also been noted in rats 

Antagonist Neurosteroids on the GABAA-Receptor
Neurosteroids may both enhance and inhibit GABAergic neurotransmission

Paradoxical effects of GABA-A modulators may explain sex steroid induced negative mood symptoms in some persons.


Some women have negative mood symptoms, caused by progestagens in hormonal contraceptives or sequential hormone therapy or by progesterone in the luteal phase of the menstrual cycle, which may be attributed to metabolites acting on the GABA-A receptor. The GABA system is the major inhibitory system in the adult CNS and most positive modulators of the GABA-A receptor (benzodiazepines, barbiturates, alcohol, GABA steroids), induce inhibitory (e.g. anesthetic, sedative, anticonvulsant, anxiolytic) effects. However, some individuals have adverse effects (seizures, increased pain, anxiety, irritability, aggression) upon exposure. Positive GABA-A receptor modulators induce strong paradoxical effects including negative mood in 3%-8% of those exposed, while up to 25% have moderate symptoms. The effect is biphasic: low concentrations induce an adverse anxiogenic effect while higher concentrations decrease this effect and show inhibitory, calming properties. The prevalence of premenstrual dysphoric disorder (PMDD) is also 3%-8% among women in fertile ages, and up to 25% have more moderate symptoms of premenstrual syndrome (PMS). Patients with PMDD have severe luteal phase-related symptoms and show changes in GABA-A receptor sensitivity and GABA concentrations. Findings suggest that negative mood symptoms in women with PMDD are caused by the paradoxical effect of allopregnanolone mediated via the GABA-A receptor, which may be explained by one or more of three hypotheses regarding the paradoxical effect of GABA steroids on behavior: (1) under certain conditions, such as puberty, the relative fraction of certain GABA-A receptor subtypes may be altered, and at those subtypes the GABA steroids may act as negative modulators in contrast to their usual role as positive modulators; (2) in certain brain areas of vulnerable women the transmembrane Cl(-) gradient may be altered by factors such as estrogens that favor excitability; (3) inhibition of inhibitory neurons may promote disinhibition, and hence excitability.

Allopregnanolone and mood disorders.


Certain women experience negative mood symptoms during the menstrual cycle and progesterone addition in estrogen treatments. In women with PMDD increased negative mood symptoms related to allopregnanolone increase during the luteal phase of ovulatory menstrual cycles. In anovulatory cycles no symptom or sex steroid increase occurs. This is unexpected as positive modulators of the GABA-A receptor are generally increasing mood. This paradoxical effect has brought forward a hypothesis that the symptoms are provoked by allopregnanolone the GABA-A receptor system. GABA-A is the major inhibitory system in the brain. Positive modulators of the GABA-A receptor include the progesterone metabolites allopregnanolone and pregnanolone, benzodiazepines, barbiturates, and alcohol. GABA-A receptor modulators are known, in low concentrations to induce adverse, anxiogenic effects whereas in higher concentrations show beneficial, calming properties. Positive GABA-A receptor modulators induce strong paradoxical effects e.g. negative mood in 3-8% of those exposed, while up to 25% have moderate symptoms thus similar as the prevalence of PMDD, 3-8% among women in fertile ages, and up to 25% have moderate symptoms of premenstrual syndrome (PMS). The mechanism behind paradoxical reaction might be similar among them who react on positive GABA-A receptor modulators and in women with PMDD. In women the severity of these mood symptoms are related to the allopregnanolone serum concentrations in an inverted U-shaped curve. Negative mood symptoms occur when the serum concentration of allopregnanolone is similar to endogenous luteal phase levels, while low and high concentrations have less effect on mood. Low to moderate progesterone/allopregnanolone concentrations in women increases the activity in the amygdala (measured with fMRI) similar to the changes seen during anxiety reactions. Higher concentrations give decreased amygdala activity similar as seen during benzodiazepine treatment with calming anxiolytic effects. Patients with PMDD show decreased sensitivity in GABA-A receptor sensitivity to diazepam and pregnanolone while increased sensitivity to allopregnanolone. This agrees with findings in animals showing a relation between changes in alpha4 and delta subunits of the GABA-A receptor and anxiogenic effects of allopregnanolone.


These findings suggest that negative mood symptoms in women with PMDD are caused by the paradoxical effect of allopregnanolone mediated via the GABA-A receptor.

Neurosteroids, GABAA receptors, and escalated aggressive behavior.


Aggressive behavior can serve important adaptive functions in social species. However, if it exceeds the species-typical pattern, it may become maladaptive. Very high or escalated levels of aggressive behavior can be induced in laboratory rodents by pharmacological (alcohol-heightened aggression), environmental (social instigation), or behavioral (frustration-induced aggression) means. These various forms of escalated aggressive behavior may be useful in further elucidating the neurochemical control over aggression and violence. One neurochemical system most consistently linked with escalated aggression is the GABAergic system, in conjunction with other amines and peptides. Although direct stimulation of GABA receptors generally suppresses aggression, a number of studies have found that positive allosteric modulators of GABAA receptors can cause increases in aggressive behavior. For example, alcohol, benzodiazepines, and many neurosteroids are all positive modulators of the GABAA receptor and all can cause increased levels of aggressive behavior. These effects are dose-dependent and higher doses of these compounds generally shift from heightening aggressive behavior to being sedative and anti-aggressive. In addition, these modulators interact with each other and can have additive effects on the GABAA receptor and on behavior, including aggression. The GABAA receptor is a heteropentameric protein that can be constituted from various subunits. It has been shown that subunit composition can affect sensitivity of the receptor to some modulators and that subunit composition differentially affects the sedative vs anxiolytic actions of benzodiazepines. Initial studies targeting alpha subunits of the GABAA receptor point to their significant role in the aggression-heightening effects of alcohol, benzodiazepines, and neurosteroids.

The Do No Harm Principle (Primum non nocere)

A guiding principle in this blog is not to do any harm, while trying to do some good.

When I read that Hardan was trialing Pregnenolone at Stanford, I thought it was very interesting, but I thought his doses were very high and did not pass the above “first, no harm” principle.  Our pediatric endocrinologist thought the dose rising to 500mg was very unwise.

When I looked into this hormone precursor a year ago I remember thinking it odd that some people were saying 5mg was a big dose, while others were using 50mg and Hardan was going up to 500mg.

Now that I have understood about the mode of action is likely GABAA, and that allopregnanolone possesses “biphasic, U-shaped actions at the GABAA receptor”, I understand what may be going on.  The tiny dose might be as effective as the huge dose, but without the side effects caused by all the other accompanying hormonal changes.

The endocrinologist would likely not worry about 5mg of Pregnenolone.  Unlike most other known PAMs of GABAA, pregnenolone does not need a prescription.

I did look for reports of people trying it themselves for schizophrenia/autism, but did not find anything useful.

Depression and  anxiety, and are frequently-seen side effects of 5α-reductase inhibitors such as finasteride, and are thought to be caused, in part, by interfering with the normal production of allopregnanolone.

Experiments in Humans

The doctors/scientist amongst you will have realized the potential therapeutic value of these paradoxical behaviors at GABAA receptors.

Instead of using the usual right hand side of the curve, where high doses are effective but may risk tolerance and side effects, we may in some cases be able to use the left hand side.  This means low doses and far less chance of any side effects.

You do of course need some data on the U curve itself and the existing levels, if any, of the chosen GABAA modulator.

In the case of pregnenolone/ allopregnanolone/progesterone this seems to exist at a constant low level in males, but in cyclical low to high levels in females.

You would need to locate where you are on the curve, or perhaps to the left of the entire curve.  By adding a positive allosteric modulator (PAM) can only move to the right.  We know that 500mg of  pregnenolone in adults move to a “better” position on the allopregnanolone curve.

In males 19-39 years old the level of Allopregnanolone is 0.8 nmol/l.

In Women  it varies from from 0.6 to 4.5 nmol/l during the month.


These results demonstrate that in response to emotional stimuli, allopregnanolone reduces activity in regions associated with generation of negative emotion. Furthermore, allopregnanolone may enhance activity in regions linked to regulatory processes. Aberrant activity in these regions has been linked to anxiety psychopathology. These results thus provide initial neuroimaging evidence that allopregnanolone may be a target for pharmacological intervention in the treatment of anxiety disorders, and suggest potential future directions for research into neurosteroid effects on emotion regulation neurocircuitry.

Pregnenolone is lipophilic and readily crosses the blood brain barrier. We have previously found that pregnenolone is preferentially metabolized to allopregnanolone, rather than other compounds such as cortisol or DHEA (43, 44); however these metabolites were also assayed. Allopregnanolone serum levels have been reported to triple two hours after oral administration of 400 mg pregnenolone (45). Thus, drug administration occurred two hours before neuroimaging to ensure elevated levels during the scan.

Pregnenolone administration reduced activity in neural circuits associated with the generation of negative emotions. Across all conditions and all face types, pregnenolone administration decreased right amygdala and right insula activity, and serum levels of pregnenolone and allopregnanolone were negatively correlated with amygdala and insula activation levels. The amygdala is a key region in threat detection (52), fear conditioning (53), and emotional salience (54). The insula is responsible for interoception (55), disgust (56), emotion processing (57), emotional recall (36), and anticipation of aversive stimuli (58). Both regions are associated with negative emotional response (57), and greater amygdala activation in response to the presentation of facial expressions is associated with greater magnitude of emotional response (5963). Additionally, activation reductions in amygdala and insula are associated with down-regulation of negative emotions (64). Thus, allopregnanolone’s reduction of activity in amygdala and insula suggests that allopregnanolone may reduce emotional reactivity to aversive stimuli.

Allopregnanolone likely impacts emotion regulation neurocircuitry through GABAergic mechanisms, though it may also impact this circuitry through its enhancement of neurogenesis (78) myelination (79) or neuroprotection (8083). Amygdala and mPFC are rich in GABA(A) receptors (28) and endogenous allopregnanolone (48), suggesting that allopregnanolone could feasibly have a direct impact on activity in these regions. Indeed, in our sample, allopregnanolone serum level was more strongly correlated to amygdala activity than activity in any other brain region. Preclinical research suggests that the amygdala may be a particular target of allopregnanolone’s anxiolytic effects (30). In rats, microinfusions of allopregnanolone directly into the amygdala produce anxiolytic (30) antidepressant (31) and anti-aggressive (32) effects. In previous neuroimaging studies, greater endogenous allopregnanolone has been reported to be associated with lower amygdala reactivity (33, 41) and greater coupling between amygdala and dmPFC (34). Though we did not directly test the GABAergic effect of our intervention, our findings illuminate potential neural pathways through which pregnenolone administration and resulting increases in allopregnanolone levels could feasibly impact GABAergic transmission in a manner that is relevant to pathological anxiety.

In conclusion, we demonstrate that pregnenolone administration (leading to increased downstream allopregnanolone levels) reduces activity in regions associated with the generation of negative emotion and enhances activity in regions linked to regulatory control over emotion, as well as increasing connectivity between two of these regions (dmPFC and amygdala). Considering the wealth of evidence that neurocircuits involving these regions are altered in anxiety disorders, our results invite further investigation into the brain basis for allopregnanolone’s use as an anxiolytic pharmacological intervention.


There is plenty of research into mood changes in females linked to the GABAA receptor.  So you could figure out what happens at what concentration of Allopregnanolone, in females.

The “problem” here is that plot thickens even further, in females it has been shown that the structure of the GABAA receptor actually changes.  When estrogen levels are higher than progesterone levels, the number of delta receptors decrease, increasing nerve cell activity, in turn increasing anxiety.

Here we demonstrate periodic alterations in specific GABA(A)R subunits during the estrous cycle in mice, causing cyclic changes of tonic inhibition in hippocampal neurons. In late diestrus (high-progesterone phase), enhanced expression of deltaGABA(A)Rs increases tonic inhibition, and a reduced neuronal excitability is reflected by diminished seizure susceptibility and anxiety. Eliminating cycling of deltaGABA(A)Rs by antisense RNA treatment or gene knockout prevents the lowering of excitability during diestrus

Since it appears the other GABAA receptors also exhibit the same U-shaped responses, there will be a choice.

I think a little experiment with very low doses of pregnenolone is worthwhile.

You may recall earlier mention in this blog of people with Asperger’s using a topical progesterone cream.  That would likely have exactly the same effect.  

There are other theories as to why progesterone cream might reduce anxiety, but it does seem to help some people.   Here is a comment on an Amazon forum:-

“My 9-year-old son is slightly autistic, suffers from severe anxiety as well as ADD, and although the medicine he takes works wonders for him, he still has residual anxiety. I rubbed 50 mg of natural progesterone cream into his chest every night for about three weeks and noticed unbelievable results. He just blossomed emotionally. We went in for his regular neuro checkup and even the neurologist immediately noticed a difference in my son, commenting on how happy and relaxed he seemed.”

There is also a pregnenolone cream.

It should be cautioned that these are all hormones and they do other things than modulate GABAA receptors.  The effect/dosage will vary between males/females and with age.


Effects of modulating multiple binding sites of GABAA

We did learn in an earlier post that the GABAA receptors have numerous different binding sites.  Since modulating some of these sites produces paradoxical results, you might wonder what happens if you really mix things up.  For example what happens if you modulate the benzo site and the neurosteroid site at the same time.


Mechanisms Underlying Tolerance after Long-Term Benzodiazepine Use: A Future for Subtype-Selective Receptor GABAA Modulators?

4.4.3. Mechanism 6: Neurosteroids
There is ample and convincing evidence that neurosteroids are endogenous allosteric regulators that interact with GABAA receptors to modulate both tonic (extrasynaptic) and phasic (synaptic) inhibition (for reviews, see [150, 151]). Also, acute or chronic neurosteroid treatment may change GABAA receptor subunit expression, especially extrasynaptic α4 and δ subunits [151]. In light of the plasticity-inducing actions of neurosteroids on inhibitory signaling, long-term enhancement of the GABA system with benzodiazepines may in turn evoke changes in the neurosteroids system such as changes in neurosteroid synthesis and metabolism, although classical benzodiazepines may differ in their potency to cause such changes [152]. In support, ovariectomy attenuated the development of tolerance to the anticonvulsant actions of diazepam [153]. Moreover, co-administration of the neurosteroids allopregnanolone or pregnenolone (but not dehydroepiandrosterone) prevented the development of tolerance after chronic treatment with either triazolam and diazepam [154]. Adding to the complexity of the putative involvement of neurosteroids in benzodiazepine tolerance, factors such as GABAA receptor subunit composition, phosphorylation mechanisms, and ((extra)synaptic) localization—which are all factors that were already found to be involved in tolerance development—influence the specific dynamics of neurosteroid activity.

Ganaxolone – an altogether better Neurosteroid ?

Ganaxolone has the same chemical structure as allopregnanolone, with the addition of a methyl group designed to prevent conversion back to an active steroid, thereby eliminating the opportunity for unwanted hormonal effects while preserving its desired CNS activity.

We came across Ganaxolone in an earlier post, which looked at drugs being trialed in Fragile X.

I thought it was interesting that it is also being trialed in epilepsy and indeed PTSD (post-traumatic stress disorder)

I think that PTSD and TBI (Traumatic Brain Injury) can provide insights for understanding autism.
It is odd that nobody has trialed Ganaxolone for schizophrenia, to see if it shares the positive effects of Pregnenolone.  Then you might expect someone to think of trialing it in autism.


It would seem that, depending on your own natural level of allopregnanolone, supplementing it with pregnenolone or progesterone could have very different effects, depending on the dosage.
In addition, we have the fact that in autism the GABAA receptor is dysfunctional and some aspects may work in reverse.

Having established that very large doses of Pregnenolone (which produces allopregnanolone) seems to be helpful in autism and schizophrenia, it would be well worth measuring the level of allopregnanolone, produced by different doses and of course investigating the effect of tiny doses of Pregnenolone.

Anecdotally, in typical people, tiny doses of Pregnenolone do have an effect.

It might turn out that because of where you are actually on the curve, you might actually need a low dose Negative Allosteric Modulator (NAM), to make you move to the left.  Interestingly there is such a NAM, Pregnenolone Sulfate.

Pregnenolone sulfate  is an endogenous excitatory neurosteroid that is synthesized from pregnenolone. It is known to have cognitive and memory-enhancing, antidepressant, anxiogenic, and proconvulsant effects.[2]


Pregnenolone sulfate is a neurosteroid with excitatory effects in the brain, acting as a potent negative allosteric modulator of the GABAA receptor and a weak positive allosteric modulator of the NMDA receptor.] To a lesser extent, it also acts as a negative allosteric modulator of the AMPA, kainate, and glycine receptors, and may interact with the nACh receptors as well. In addition to its effects on ligand-gated ion channels, pregnenolone sulfate is an agonist of the sigma receptor, as well as an activator of the TRPM1 and TRPM3 channels. It may also interact with potassium channels and voltage-gated sodium channels.

Pregnenolone and its sulfate, like DHEA and its sulfate and progesterone, belong to the group of neurosteroids that are found in high concentrations in certain areas of the brain, and are synthesized there. Neurosteroids affect synaptic functioning, are neuroprotective, and enhance myelinization. Pregnenolone and its sulfate ester are under investigation for their potential to improve cognitive and memory functioning.[3] Pregnenolone is also being considered as a potential treatment for schizophrenia.[1]
“Studies in animals demonstrated that the neurosteroids pregnenolone (PREG) and dehydroepiandrosterone (DHEA), as sulfate derivatives (PREGS and DHEAS, respectively), display memory-enhancing properties in aged rodents. Moreover, it was recently shown that memory performance was correlated with PREGS levels in the hippocampus of 24-month-old rats. Human studies, however, have reported contradictory results. First, improvement of learning and memory dysfunction was found after DHEA administration to individuals with low DHEAS levels, but other studies failed to detect significant cognitive effects after DHEA administration. Second, cognitive dysfunctions have been associated with low DHEAS levels, high DHEAS levels, or high DHEA levels; while in other studies, no relationship was found.”

Another NAM at the GABAA receptor is DHEA, a steroid hormone produced in the body.  Regular exercise stimulates the production of DHEA.

We also learnt that structure of the GABAA receptor can be modified.  It happens continuously in females.  So as well as clever ways to use allosteric modulators, you could also copy nature and change the structure of the GABAA receptors themselves.  In fact the genetic research does suggest this structure has been disturbed in autism; you would just be correcting a defect.

It does look like high dose Pregnenolone really is effective in reducing the symptoms in schizophrenia.  Here is yet another study showing this:-