It’s not Autism, it’s Sotos Syndrome – and more about GABA therapies

 Peter the wild boy, with Pitt Hopkins Syndrome

I recently returned from a 25 year class reunion; of the 200 or so class members about 120 turned up. Of the 200 we know that at least 5 have a son with autism and at least one has a nephew with autism.  So I had my first ever “autism lunch” discussing all those tricky issues we are left to deal with.

What was immediately apparent was how different each child’s “autism” was and that none of them were the autism-lite variants that are now being so widely diagnosed in older children. or even adults .  Of the six, two are non-verbal, one is institutionalized, yet one talks a lot.  Three sets of parents are big ABA fans and one child did not respond to ABA.

You may be wondering about that high incidence of autism.  This was not a gathering of science boffins or mathematicians; this was at a business school.  One thing is obvious, you can correlate some autism incidence with educational level.  You can connect all sorts of measures of IQ to autism, from having a math prodigy in the family, to having professors at Ivy league type Universities, particularly in Mathematics.  It does appear to be true that the so-called clever genes are also associated with some types of autism.

I presume that if my science-only university organized such events the incidence of autism would be even higher.

On the way back home we met an acquaintance at the airport, who was telling us all about his son with Sotos Syndrome.  "It is not autism", we were informed, but then I am not quite sure what is.  When you look it up, many of the symptoms look just like autism.  In fact, it is a single gene dysfunction that leads to gigantism and various elements of autism.

This brings me to the painting above of Peter the Wild Boy; it is not me I should point out.  The above Peter was a German boy who came to live in England in the 18^th Century; he was non-verbal and is now thought to have had Pitt Hopkins Syndrome.  Like Sotos, this is another very rare single gene disorder.

We have already come across Rett Syndrome, which for some reason is treated as autism.

Fragile X is thought of as a syndrome where autism can be comorbid.

Timothy Syndrome is fortunately extremely rare, but I have already drawn on it in my own research into autism.

There are also autism related disorders involving multiple genes.

Prader–Willi syndrome  is a rare genetic disorder in which seven genes (or some subset thereof) on chromosome 15 (q 11–13) are deleted or unexpressed (chromosome 15q partial deletion) on the paternal chromosome.  If the maternally derived genetic material from the same region is affected instead, the sister Angelman Syndrome is the result.

The most frequent disorder caused by known multiple gene overexpression is Down Syndrome.  We saw in earlier post that DS is caused by the presence of all or part of a third copy of chromosome 21.  This results in over-expression of some 300 genes.

Why So Many Syndromes

Even before the days of genetic testing, these syndromes had been identified.  How could that be?  Each syndrome is marked by clear physical differences.

These physical differences where used to identify those affected.

Within autism too, sometimes there are physical differences.  Big heads, small heads, slim stature or heavy stature, advanced bone age or retarded bone age.

So many syndromes , but no therapies

Many of the rare syndromes have their own foundations funding research, mainly on the basis that if there is a known genetic dysfunction there should be matching therapy somewhere.

As of today, there are no approved therapies for any of these syndromes.

The Futility of Genetic Research?

A great deal of autism research funding goes into looking for target genes.  The idea goes that once you know which gene is the problem you can work out how to correct it.  There are numerous scientific journal dedicated to this approach.

Since no progress has been made in treating known genetic conditions leading to “autism”, is all this research effort well directed?  Some clever researchers think it is not.

All I can do is make my observations from the side lines.

What do Down Syndrome, Autism and Pitt Hopkins Syndrome all have in common?

In at least some of those affected, they have the identical excitatory-inhibitory imbalance of GABA, that can be corrected by Bumetanide.

If you did whole exome genetic testing on the responders with these three conditions you would not find a common genetic dysfunction; and yet they respond to the same therapy.

I am actually all for continued genetic research, but those involved have got to understand its limitations, as well as its potential.

More on GABA

This post returns to the theme of the dysfunctional GABA neurotransmitter because the research indicates it is present in numerous of the above-mentioned conditions. 

Table 1.  Summary of GABAA signaling alterations in neurodevelopmental disorders (click for the full Table)

·        Autism

·        Fragile X

·        Rett Syndrome

·        Down Syndrome

·        Neurofibromatosis type 1

·        Tourette syndrome

·        Schizophrenia

·        Tuberous sclerosis complex (TSC)

·        Prader-Willi syndrome

·        Angelman Syndrome

Based on feedback to me, we should add Pitt Hopkins Syndrome to the above list.

The GABA dysfunction is not the same in all the above conditions, but at least in some people, Bumetanide is effective in cases of autism, Down Syndrome and Pitt Hopkins Syndrome.  I suspect that since it works in mice with Fragile-X , it will work in at least some humans.

GABA_A has already been covered in some depth in this blog, but I am always on the lookout for more on this subject, since interventions are highly effective.  It is complicated, but for those of you using Bumetanide, Low Dose Clonazepam, Oxytocin and some even Diamox, the paper below will be of interest.

Modulation of GABAergic transmission indevelopment and neurodevelopmental disorders: investigating physiology andpathology to gain therapeutic perspectives

Regular readers will know that in autism high levels of chloride Cl⁻ inside the neuron have been shown to make GABA excitatory rather than inhibitory.  This leads to neurons firing too frequently;  this results in effects ranging from anxiety to seizures and with reduced cognitive functioning.  Therapies revolve around reducing chloride levels, this can be done by restricting the flow in ,or by increasing the flow out.  The Na⁺/K⁺/Cl⁻ cotransporter NKCC1  imports Cl⁻ into the neuron.  By blocking this transporter using Bumetanide you can achieve lower Cl⁻ within the neuron, but with this drug you also affect NKCC2, an isoform present in the kidney, which is why Bumetanide is a diuretic.  Some experimental drugs are being tested that block NKCC1 without affecting NKCC2 and better cross the blood brain barrier. 

The interesting new approach is to restore Cl⁻ balance by increasing KCC2 expression at the plasma membrane.  This means increasing the number of transporters that carry  Cl⁻  out of the neurons.

Chloride extrusion enhancers as novel therapeutics for neurological diseases

In the Modulation of GABAergic transmission paper there is no mention of acetazolamide (Diamox) which I suggested in my posts could also reduce Cl⁻, but via the AE3 exchanger.  This would explain why Diamox can reduce seizures in some people.

The paper does mention oxytocin and it does occur to me that babies born via Cesarean/Caesarean section will completely miss this surge of the oxytocin hormone.  This oxytocin surge is suggested to be key to the GABA switch, which should occur soon after birth when GABA switches from excitatory to inhibitory.  In much autism this switch never takes place.

That would suggest that perhaps all babies born via Caesarean section should perhaps receive an artificial dose of oxytocin at birth.  This might then reduce the incidence of GABA dysfunctions in later life, which would include autism and some epilepsy.

Indeed, children born by Caesarean section (CS) are 20% more likely to develop autism.

Association Between Obstetric Mode of Delivery and Autism Spectrum Disorder - :  A Population-Based Sibling Design Study

Conclusions and Relevance  This study confirms previous findings that children born by CS are approximately 20% more likely to be diagnosed as having ASD. However, the association did not persist when using sibling controls, implying that this association is due to familial confounding by genetic and/or environmental factors.

So as not to repeat the vaccine/autism scare, the researchers do not say that Caesarean section leads to more autism, rather that the kinds of people who are born by Caesarean section already had an elevated risk of autism.  This is based on analysing sibling pairs, but I do not entirely buy into that argument.  They do not want to scare people from having a procedure that can be life-saving for mother and baby.

If you look at it rationally, you can see that the oxytocin surge at birth is there for an evolutionary reason.  It is very easy to recreate it with synthetic oxytocin.

Another interesting point is in the conflict of interest statement:-

Laura Cancedda is on the Provisional Application: US 61/919,195, 2013. Modulators of Intracellular Chloride Concentration For Treating An Intellectual Disability

Regular readers will note that in this blog we have known for some time that modifying GABA_A leads to improved cognitive function.  I even suggested to Ben-Ari that IQ should be measured in their autism trials for Bumetanide.  IQ is much less subjective than measures of autism.

Conclusion

My conclusion is that while genetic testing has its place, it is more productive to look at identifying and treating the downstream dysfunctions that are shared by many individual genetic dysfunctions.

By focusing on individual genes there is a big risk of just giving up, so if you have Pitt Hopkins Syndrome, like Peter the Wild Boy, it is a single gene cause of “autism” and there is no known therapy.  Well it seems that it shares downstream consequences with many other types of autism, so it is treatable after all.

I also think more people need to consider that cognitive dysfunction (Intellectual Disability/MR) may indeed be treatable, and not just via GABA; so good luck to Laura Cancedda.

OPN-300 Oxytocin and Autism

This post is about nasal spray drugs and Oxytocin.

Monty, aged 12 with ASD, uses a conventional anti-histamine nasal spray and I do sometimes wonder just how much of the drug reaches its target.  

With inhalers for asthma this is a well known problem and often even adults do not use them correctly; they are proven to work much better when they are fitted with a spacer chamber, that way the drug ends up in your lungs and not stuck to the inside of your mouth.

Many adults with asthma and COPD nowadays use spacers.

So my interest was drawn to a company called Optinose that is developing drugs for nasal delivery using a novel dispenser.  I was particularly surprised that in its small drug pipeline is an oxytocin spray for autism.

If you look on the US National Institute of Health website listing clinical trials of oxytocin and autism, you will find that thirty, yes three zero, studies are listed.

According to their website, Optinose intend to be the first to bring a product to the market approved for autism.

On the clinical trials website you may notice that other trials use an existing drug called Syntocinon that is a synthetic form of Oxytocin already approved for other purposes.

I did mention in an earlier post that the US rights to Syntocinon were sold to a company hoping to develop a therapy for Schizophrenia and Autism.

Retrophin Signs U.S. License Agreement for Syntocinon™ Nasal Spray (Oxytocin)

In Europe Syntocinon is available in most countries as a prescription drug.


The Optinose idea is that their dispenser can much more reliably dispense the correct amount of drug and have it reach the membrane deep inside the nose.  None gets in the mouth and less should get stuck at the entrance to the nose.

Previous trials of Oxytocin have yielded very mixed results.  Perhaps part of this is due to the nature of the spray pump being used?  It is certainly plausible.

The Optinose Spray

The Optinose spray is inserted in one nostril and your mouth.  You blow out through mouth, sealing the nasal cavity in the process, and the spray is forced out into your nose.  This should ensure it goes deep inside to the nasal membrane, where the oxytocin can cross directly into the blood stream.

Click on the link below and then click to play the short video.

http://www.optinose.com/optinose-platform/technical-overview

As the video points out, this kind of drug delivery can “enable new and improved brain treatments”

They are talking about direct nose-to-brain drug delivery, bypassing the blood brain barrier (BBB).  This is not fantasy and is already quite well studied.

Direct nose to brain drug delivery via integrated nerve pathways bypassing the blood-brain barrier: an excellent platform for brain targeting.

Coming back to Oxytocin ...

Not only is Oxytocin a well-known hormone affecting social behavior, but it also plays a role in switching the neurotransmitter GABA between excitatory and inhibitory.

Oxytocin and GABA_A

Oxytocin has a role at birth in the GABA “switch”, but it also has an ongoing role via binding to a particular subunit of GABA_A receptors.

Oxytocin-Mediated GABA Inhibition During Delivery Attenuates Autism Pathogenesis in Rodent Offspring

We report that the oxytocin-mediated neuroprotective γ-aminobutyric acid (GABA) excitatory-inhibitory shift during delivery is abolished in the valproate and fragile X rodent models of autism. During delivery and subsequently, hippocampal neurons in these models have elevated intracellular chloride levels, increased excitatory GABA, enhanced glutamatergic activity, and elevated gamma oscillations. Maternal pretreatment with bumetanide restored in offspring control electrophysiological and behavioral phenotypes. Conversely, blocking oxytocin signaling in naïve mothers produced offspring having electrophysiological and behavioral autistic-like features. Our results suggest a chronic deficient chloride regulation in these rodent models of autism and stress the importance of oxytocin-mediated GABAergic inhibition during the delivery process. Our data validate the amelioration observed with bumetanide and oxytocin and point to common pathways in a drug-induced and a genetic rodent model of autism.

Further evidence as to the precise effect of Oxytocin on GABA receptors was found by chance.  It was found that having dosed rats with Oxytocin, they did not get drunk when fed alcohol.

Oxytocin prevents ethanol actions at δsubunit-containing GABAA receptors and attenuates ethanol-induced motor impairment in rats

Specifically, oxytocin (1 µg i.c.v.) given before ethanol (1.5 g/kg i.p.) attenuated the sedation and ataxia induced by ethanol in the open-field locomotor test, wire-hanging test, and righting-reflex test in male rats.

Vasopressin, which is a nonapeptide with substantial structural similarity to oxytocin, did not alter ethanol effects at δ-GABA_ARs. This pattern of results confirms the specificity of the interaction between oxytocin and ethanol at δ-GABA_ARs

The profound and direct interaction observed between oxytocin and ethanol at the behavioral and cellular level may have relevance for the development of novel therapeutics for alcohol intoxication and dependence.

Is Oxytocin a useful Autism Therapy?

Given the large number of trials and the number of people already taking Oxytocin, some people clearly believe in the therapeutic potential of Oxytocin.

What is clear is that there a numerous modes of action for Oxytocin, some of which relate to GABA_A receptors.

So why is it taking so very long for these trials to come to any usable conclusion? Well just looking at the long list of researchers, it includes some of those who have spent twenty years "researching" autism and producing absolutely nothing tangible, just papers concluding more research is needed or even producing, supposedly therapeutic, cartoons (Cambridge University).

We have the usual problem that numerous different dysfunctions lie at the root of “autism” and so only a moderate proportion, at best, would be expected to benefit from any therapy.

In the case of nasal sprays we have the question of how much actually gets delivered to the right place deep inside the nose where there is a very thin membrane that allows the Oxytocin to cross over into the blood.

OPN-300 Clinical Trials

The Phase 1 trial for OPN-300 was actually on healthy adults, and looked at things like dosing.  Low doses were more effective than high doses.  Next follows the trial on people with autism.  

Low-dose oxytocin delivered intranasally with Breath Powered device affects social-cognitive behavior: a randomized four-way crossover trial with nasal cavity dimension assessment

Despite the promise of intranasal oxytocin (OT) for modulating social behavior, recent work has provided mixed results. This may relate to suboptimal drug deposition achieved with conventional nasal sprays, inter-individual differences in nasal physiology and a poor understanding of how intranasal OT is delivered to the brain in humans. Delivering OT using a novel ‘Breath Powered’ nasal device previously shown to enhance deposition in intranasal sites targeted for nose-to-brain transport, we evaluated dose-dependent effects on social cognition, compared response with intravenous (IV) administration of OT, and assessed nasal cavity dimensions using acoustic rhinometry. We adopted a randomized, double-blind, double-dummy, crossover design, with 16 healthy male adults completing four single-dose treatments (intranasal 8 IU (international units) or 24 IU OT, 1 IU OT IV and placebo). The primary outcome was social cognition measured by emotional ratings of facial images. Secondary outcomes included the pharmacokinetics of OT, vasopressin and cortisol in blood and the association between nasal cavity dimensions and emotional ratings. Despite the fact that all the treatments produced similar plasma OT increases compared with placebo, there was a main effect of treatment on anger ratings of emotionally ambiguous faces. Pairwise comparisons revealed decreased ratings after 8 IU OT in comparison to both placebo and 24 IU OT. In addition, there was an inverse relationship between nasal valve dimensions and anger ratings of ambiguous faces after 8-IU OT treatment. These findings provide support for a direct nose-to-brain effect, independent of blood absorption, of low-dose OT delivered from a Breath Powered device.

Importantly, the current findings are the first to suggest that a low dose of OT is more effective than a higher dose in modulating social cognition

Converging biological and behavioral evidence suggests that lower OT doses may be more efficacious than higher doses. For instance, compared with higher doses, lower doses increased peripheral levels of OT in saliva,⁶⁵ attenuated cortisol stress responses⁶⁶ and increased eye gaze in patients with Fragile X syndrome.⁶⁷ In animals, a low dose of OT administered shortly after birth increased partner preference later in life, whereas higher doses did not.⁶⁸ Similarly, lower doses have been associated with stronger increases in social recognition compared with higher doses.^{69, 70} The dose–response data reported here provide useful preliminary evidence concerning the optimal dose for social cognition modulation; however, extrapolation from healthy individuals to patients must be with caution. Patients with social-cognitive deficits may respond differently than healthy volunteers, so future studies should explore effects in patient populations to determine the generalizability of these findings to target illnesses. Future work should also further investigate the role of different delivery devices, administration routes, dosages and social cognition tasks on the efficacy of intranasal OT, ideally using larger sample sizes given the limitation of a relatively small sample size in the present study.

In addition, this study provides preliminary evidence that a lower dose (8 IU) may offer greater efficacy than a higher dose (24 IU) when administered with the Breath Powered device.

There are a number of interpretations regarding why no effect was observed at the 24 IU OPN-OT dose, in contrast to the 8 IU dose. For example, a higher OT dose is more likely to influence the balance of AVP/OT, as evidenced by the decrease in AVP concentration after 24 IU OPN-OT (but not 8 IU OPN-OT) observed in the present study, which can modulate social behavior.

OptiNose reports positive results from Phase 1 trial of intranasal oxytocin for autism

Jul 15 2015

OptiNose has announced that a study comparing OPN-300 intranasal oxytocin to intravenous oxytocin for the treatment of autism showed the achievement of similar blood levels but significantly greater social-cognitive effects after intranasal administration. The results were published online July 14, 2015 in Translational Psychiatry.

The randomized, placebo-controlled, double-blind, double-dummy, 4-arm cross-over study involved 16 healthy volunteers who received either intravenous oxytocin or two doses of OPN-300 delivered using OptiNose’s bi-directional breath powered intranasal delivery device. Social-cognitive effects were measured by emotional rating of facial images.

Researcher Ole A. Andreassen of the University of Oslo said, “The OptiNose technology significantly changes the way drug is delivered high up in the nose, and may be the drug delivery solution we’ve been looking for. If we can improve social cognition in healthy people with OPN-300 low-dose oxytocin, then we may be able to address a core symptom suffered by millions of patients worldwide with autism.”

OptiNose Chief Scientific Officer Per Djupesland commented, “Although animal data has been encouraging, many would argue that medication transport from the nasal cavity directly to the brain has not been previously proven in humans. Today’s results are quite promising and bolster our belief that we can enable and enhance the treatment of common brain disorders with OptiNose delivery technology.”

The company says that it is initiating a Phase 2 trial of OPN-300 in autism patients in Norway. OptiNose is also developing intranasal fluticasone for chronic sinusitis and recently reported positive results from a Phase 3 trial of that product.

Read the OptiNose press release.

Read the Translational Psychiatry article.

Conclusion

Some parents already use the Syntocinon version of oxytocin for autism; some tried it in one of the earlier clinical trials and found it did not help.  There is nothing surprising in that. 

The people at OptiNose seem to be a bit more motivated than some of the other oxytocin researchers, in relaxed leafy universities, to actually get to the finishing line.  They are initiating Phase 2 trials of OPN-300 in autism patients in Norway.  Some of the other studies have been going on for several years and are still not finished.

Hopefully we will soon have some data on what percentage of people with “autism” respond to OPN-300 and then we could compare that to the response to Syntocinon.

As we have seen several times before, it seems that smaller doses of oxytocin are more effective than larger doses.  Larger doses seem to change (reduce) vasopressin levels, which will also affect social behavior.

One you start changing the level of one hormone, like oxytocin, you are very likely to affect others.  There are many interrelations and feedback loops.  

Oxytocin may well be part of the solution for some people with autism, but I expect in others it may make them worse.  Hopefully in the later trial(s) they will try and indentify biomarkers for the responder group.

Tuning GABAa receptors, plus Oxytocin

Today’s post will hopefully not get too complicated.

As has been mentioned in this blog, and also at leading institutions like MIT, it does seem possible to fine-tune certain receptors in the brain that have become dysfunctional in autism.  In the case of MIT they were “tuning” a receptor called mGluR5, which they suggested was either hypo or hyper, in other words too much or too little, depending on what the underlying disease variant was.

This was done with something called an allosteric modulator, either a positive one called PAM, or a negative one called NAM.

They found that a particular glumate receptor, called mGluR5, was dysfunction in many autism-like conditions.  But the nature of the dysfunction varied, so different people would require different treatments to return the receptor performance back to normal (top dead center).   So it really becomes like tuning your car engine. 

As I have progressed in my review of the literature it becomes clear that numerous receptors are “out of tune”; so a better analogy is tuning something like a piano.

  

Ketamine, Memantine, D-Cycloserin, Magnesium, Fenobam and yet more as Glutamatergic Modulators in Autism (and Fragile X)

"Tuning" the shape (but not number) of dendritic spines also appears not to be as fanciful as it sounds.

Back to GABA_A

Regular readers will know that one of the key dysfunctional receptors in autism is called GABA_A.

GABA A Receptors in Autism – How and Why to Modulate Them

This subject is very complicated.  In effect what appears to have happened in autism is that the neurons have not matured as they should, and so GABA_A receptors continue to function in their “normal” immature state.  The concentration of chloride remains high since the NKCC1 transporter continues to exist, whereas KCC2/3 should have developed.  The result is that when the receptor is stimulated, instead of causing an inhibitory/calming effect it causes an excitatory effect.

This is fortunately treatable by inhibiting the flow of chloride into the cells, through NKCC1, using a drug called Bumetanide.

However this is not the end of the story.

At least 11 binding sites on GABA_A receptors

As you can learn from Wikipedia:-

The active site of the GABA_A receptor is the binding site for GABA and several drugs such as muscimol, gaboxadol, and bicuculline. The protein also contains a number of different allosteric binding sites which modulate the activity of the receptor indirectly. These allosteric sites are the targets of various other drugs, including the benzodiazepines, nonbenzodiazepines, barbiturates, ethanol, neuroactive steroids, inhaled anaesthetics, and picrotoxin, among others.

We are particularly interested in the allosteric binding sites.

The only one that is usually referred to, in any depth, is the site for benzodiazepines, but there are at least 11 different binding sites.

GABAa receptor pharmacology.

Abstract

gamma-Aminobutyric acid (GABA)a receptors for the inhibitory neurotransmitter GABA are likely to be found on most, if not all, neurons in the brain and spinal cord. They appear to be the most complicated of the superfamily of ligand-gated ion channels in terms of the large number of receptor subtypes and also the variety of ligands that interact with specific sites on the receptors. There appear to be at least 11 distinct sites on GABAA receptors for these ligands.

Development of Subtype-Selective GABAA Receptor Compounds for the Treatment of Anxiety, Sleep Disorders and Epilepsy

These sites include:-

·        GABA Binding Site

·        Benzodiazepine Binding Site

·        Neurosteroid Binding Site

·        Convulsant Binding Site

·        Barbiturate Binding Site

·        b Subunit Binding Site(s)

In an earlier post I highlighted the discovery by Professor Catterall, that tiny doses of a particular Benzodiazepine drug called Clonazepam had a strange effect on the GABA_A receptor.

Clonazepam is a known Positive Allosteric Modulator (PAM) of the GABA_A site.  In mature neurons it amplifies the calming effect when the GABA binding site is stimulated.  In mouse models of autism (we assume therefore immature neurons)   where GABA is still excitatory, the tiny dose seemed to switch it to inhibitory.

This suggests a new function, rather than a PAM, the effect was to invert the function entirely.

Now it appears that similar things may indeed also be possible at some of the other 9+ binding sites (I exclude GABA Binding Site itself)

As complicated as this subject may sound, it actually gets even more complicated since the GABA receptors are made up of sub-units.  It appears that mutations in these subunits may be a cause of some epilepsies and, I propose, some “oddities” in autism.

Recent studies have again shown that many genetic dysfunctions found in autism relate to GABA, this short article is not so recent, but gives a nice summary:-

GABA is the major inhibitory neurotransmitter in the brain. It essentially acts as a brake for brain activation. Several aspects of GABA regulation have been linked to ASD, from early brain development to adult brain function.

Variations in GABA receptor subunits have been strongly associated with ASD. GABA receptors come in two major forms: fast, “ionotropic” GABAA receptors let negatively charged chloride ions flow into the neuron, and slow, “metabotropic” GABAB receptors produce chemical messages inside the neuron. GABAA receptors, the most common form in the brain, contain five subunits that shape their properties. Genome-wide association studies have linked the GABAA receptor subunit genes GABRA4 (α4 subunit), GABRB1 (β1 subunit), and GABRB3 (β3 subunit) to autism.[1][2] In addition, deletion of a chromosomal region that contains a cluster of a variety of GABA receptor genes (region 15q11-13) causes Angelman Syndrome.[3][4]

Genes controlling the development of GABA-releasing neurons have also been associated with ASD. Autism-linked variations in the ARX and DLX family of transcription factors interfere with proper expression of GABA.[5][6][7] Absence of such GABA-releasing neurons would negatively affect early brain development as well as adult brain stability.

Notably, variations in other ASD-linked genes affect GABA signaling. New evidence shows that the gene MECP2, the mutation of which causes Rett Syndrome, is critical for normal function of GABA-releasing neurons.[8] When MECP2 expression was blocked in GABAergic neurons of mice, GABA expression and release were reduced and the mice exhibited autistic behaviors.

ASD is a complex disorder that is likely to be caused by a combination of mutations in a variety of genes. GABA receptors are a promising therapeutic target because of their important role in monitoring brain excitation. Identification and exploration of autism-linked mutations in other GABA-related genes could shed light on the pathogenesis of autism.

Over to Switzerland

At the University of Bern a small research group is looking  at the world of  GABA_A receptors, here is what they say:-

“Many scientists and companies are put off by the complexity of the field of GABA_A receptors, but it is exactly this complexity that offers numerous possibilities of fine-tuned pharmacological interventions.” 

Prof.Dr. Erwin Sigel

Here is one of their recent papers, that shows both what is known and how very much remains unknown.

Structure, Function, and Modulation of GABAA Receptors

Ion Conductance

The GABA_A receptors are generally GABA-gated anion channels selective for Cl⁻ ions, with some permeability for bicarbonate anions (49). Exceptionally, in C. elegans, a cation-selective GABA-gated channel has been discovered (50). Excitatory neurotransmitters increase the cation conductance to depolarize the membrane, whereas inhibitory neurotransmitters increase the anion conductance to tendentially hyperpolarize the membrane. However, if the gradient for Cl⁻ ions decreases due to down-regulation of KCC2 chloride ion transporters, opening of GABA_A receptors may cause an outward flux of these anions, leading to depolarization of the membrane and thereby to excitation. This phenomenon has been implicated in neuropathic pain (51). During early development (52) and in neuronal subcompartments (53), GABA similarly confers excitation. 

Although it is relatively simple to address questions at the level of individual receptor subunit isoforms, we can only speculate how many GABA_A receptors are expressed in our brain and what their subunit composition is, not to mention subunit arrangement.

Conclusions

Many scientists and companies are put off by the complexity of the field of GABA_A receptors, but it is exactly this complexity that offers numerous possibilities of fine-tuned pharmacological interventions.

It may be anticipated that genetic alterations of subunits of the GABA_A receptor affect any of the above mentioned processes and thereby contribute to inherited human diseases. A start has been made with the analysis of point mutations that cause epilepsy

Mutations in GABAA receptor subunits associated with genetic epilepsies

Why is all this relevant ?

We have in recent posts discovered that at least two anti-convulsants (carbamazepine and phenytoin) appear to modulate GABAA receptors in unexpected ways when given in tiny doses.

We also found out that valproate also seems to possess such qualities.  The exact mode of action of valproate is not known and perhaps it also acts a modulator of one of the many binding sites on the GABAA receptors.

We do think that valproate is working somehow via GABA.

Modulation of the gamma-aminobutyric acid type A receptor by the antiepileptic drugs carbamazepine and phenytoin

It turns out that Carbamazepine has also been shown to potentiate GABA receptors made up of alpha1, beta2, and gamma2 subunits.

I have already established that the effect of tiny doses of Valproate is not the same as tiny doses of Clonazepam.

The next step would be to look at the effect of tiny doses of carbamazepine, phenytoin and potentially anything else that modulates those mysterious  GABA_Asites.  They are clearly all there for a reason.  It seems that their role goes beyond just the allosteric modulation (amplification/reduction) of GABA’s effect.  It is likely much more subtle and they affect emotional behaviour.

Given the difficulty/impossibility of research on human brains, in the end we may need to revert to the medical world’s often used “scientific” discovery methods known as trial and error, and stumbled upon.

For the moment that will be left to Professors Sigel and Catterall and their mice, and Dr Bird, in Australia, with his human subjects.

Oxytocin and Bumetanide share the same mode of action in autism

Whilst on the subject of GABA_A, I should come back to Oxytocin.

Oxytocin-Mediated GABA Inhibition During Delivery Attenuates Autism Pathogenesis in Rodent Offspring

The conclusion of this Ben-Ari paper from last year is that Oxytocin and Bumetanide share the same effect in autism; they lower the level of chloride within the neurons and help switch GABA back to inhibitory.

It seems that oxytocin from the mother may be the signal to the developing brain to lower Cl levels.  Oxytocin has many other functions in the body.

Small doses of oxytocin/Syntocinon, have been shown to be effective in some people with autism.  One reader from Portugal has written on this blog how effective it has been in his young son.

Oxytocin/Syntocinon is not available everywhere, but is being reintroduced to the US.

Retrophinto reintroduce Syntocinon™ Nasal Spray in the U.S. and Develop the Drug for Schizophrenia and Autism

I am wondering if in some people, who are not responders, bumetanide/oxytocin lowers the level of chloride, but not enough to show any benefit.  People using Bumetanide, which has a short half-life, comment that the effect fades through the day and that splitting the same daily dose 3 times a day is beneficial over 2 times a day.  This might suggest that combining Oxytocin with Bumetanide might give better results, by maintaining the downward pressure on chloride levels and keeping GABA more inhibitory and for longer.

In the longer term, an analog of Bumetanide is needed without the diuretic effect and with a delayed release, to maintain a constant effective level.  This is known to the researchers, but would require a big financial investment.

Larger doses of oxytocin are likely to produce effects elsewhere in the body.

If anyone tries the combination of Bumetanide + oxytocin, let me know.