Italy has many attractions, one being Lake Como (Villa Clooney).
It is also the only western country still using Cardiazol, where it is used in a cough medicine
Varanasi and the Ganges, not a place you could forget, particularly the smell.
India is the only other country using Cardiazol
Today’s post draws on clever things going on in Down Syndrome research to improve cognitive function, but puts them in the perspective of the faulty GABA switch.
In the United States it is estimated that 250,000 families are affected by Down Syndrome. It is caused by a third copy of chromosome 21, resulting in up-regulation of around 300 genes. A key feature is low IQ, this is partly caused by a physically smaller cerebellum and it appears partly by the GABA switch. Research has shown that the cerebellum growth could be normalized, but this post is all about the GABA switch.
In an earlier very science heavy post we saw how a faulty GABA switch would degrade cognitive function in many people with autism, schizophrenia or Down Syndrome. Basmisanil is a drug in Roche’s development pipeline.
More evidence to show the GABA switch affects schizophrenia was provided by our reader Natasa.
Perturbations of γ-aminobutyric acid (GABA) neurotransmission in the human prefrontal cortex have been implicated in the pathogenesis of schizophrenia (SCZ), but the mechanisms are unclear. NKCC1 (SLC12A2) is a Cl--importing cation-Cl- cotransporter that contributes to the maintenance of depolarizing GABA activity in immature neurons, and variation in SLC12A2 has been shown to increase the risk for schizophrenia via alterations of NKCC1 mRNA expression. However, no disease-causing mutations or functional variants in NKCC1 have been identified in human patients with SCZ. Here, by sequencing three large French-Canadian (FC) patient cohorts of SCZ, autism spectrum disorders (ASD), and intellectual disability (ID), we identified a novel heterozygous NKCC1 missense variant (p.Y199C) in SCZ. This variant is located in an evolutionarily conserved residue in the critical N-terminal regulatory domain and exhibits high predicted pathogenicity. No NKCC1 variants were detected in ASD or ID, and no KCC3 variants were identified in any of the three neurodevelopmental disorder cohorts. Functional experiments show Y199C is a gain-of-function variant, increasing Cl--dependent and bumetanide-sensitive NKCC1 activity even in conditions in which the transporter is normally functionally silent (hypotonicity). These data are the first to describe a functional missense variant in SLC12A2 in human SCZ, and suggest that genetically encoded dysregulation of NKCC1 may be a risk factor for, or contribute to the pathogenesis of, human SCZ.
This study showed that some with schizophrenia will likely benefit from Bumetanide, but that the underlying reason for excessive NKCC1 activity in schizophrenia is not the same as in ASD. Different cause but the same end result and the same likely therapy, repurposing an old existing drug.
α3 and α5 sub-units of GABAA
The science is rather patchy, but it seems that the α3 sub-unit of GABAA receptors is under-expressed in some autism and there is a fair chance that the α5 sub-unit is correspondingly over-expressed.
We know that over-expression of α5 is associated with cognitive impairment.
Down regulating α5 is currently a hot topic in Down Syndrome and at least two drugs are in development.
Reading the Down Syndrome research suggests that those involved have not really understood what is going on. They do seek to modify GABA signaling, but have not realized that likely problem is the miss-expression of GABAA subunits in the first place, exactly as in autism. As in autism, this faulty “GABA switch” has more than one dimension. An incremental benefit can be expected from correcting each one.
Further support for the use of low dose Clonazepam in some Autism
In previous posts we saw how Professor Catterall's idea to use low dose clonazepam to treat some autism does translate from mice to humans. This was based on up-regulating the α3 sub-unit of GABAA receptors.
There is some new research on this subject and Japanese research
is very often of the highest quality.
In the paper
below, highlighted by our reader Tyler, they use low dose clonazepam to reduce
autistic behavior in a rare condition called Jacobsen syndrome. While Professor Catterall and several readers
of this blog are using low dose clonazepam to upregulate the α3 sub unit of
GABAA receptors, the Japanese
attribute the benefit to the γ2 subunit.
Whichever way you look
at it, another reason to support trial of low dose clonazepam in autism. When I say low, I mean a dose 100 to 1,000
times lower than the standard doses.
Jacobsen
syndrome (JBS) is a rare congenital disorder caused by a terminal deletion of
the long arm of chromosome 11. A subset of patients exhibit social behavioural
problems that meet the diagnostic criteria for autism spectrum disorder (ASD);
however, the underlying molecular pathogenesis remains poorly understood.
ASD-like
behavioural abnormalities in PX-RICS-deficient
mice are ameliorated by enhancing inhibitory synaptic transmission with a GABAAR agonist
(Clonazepam)
A curative effect
of clonazepam on autistic-like behaviour
These results
demonstrate that ASD-like behaviour in PX-RICS−/− mice
is caused by impaired postsynaptic GABA signalling and that GABAAR
agonists have the potential to treat ASD-like behaviour in JBS patients and
possibly non-syndromic ASD individuals.
“Correcting GABA” in Down Syndrome
I expect there may be four different methods, all relating to GABAA, to improve cognition in Down Syndrome just as there appear to be in autism:-
· Reduce intracellular Cl- by blocking NKCC1 with bumetanide
· Down regulate α5 sub-units of GABAA
· Damp down GABAA receptors with an antagonist
· Upregulate α3 sub-units of GABAA
Two of the above are being pursued in Down Syndrome research, but two do not seem to be.
Enhancing Cognitive Function in Down Syndrome
These are the sort of headlines that appeal to me:-
Cognitive-enhancing drugs may have a significant impact, doctors say. An IQ boost of just 10 to 15 points could greatly increase the chance that someone with the syndrome would be able to live independently as an adult, said Brian Skotko, co-director of the Down syndrome program at Massachusetts General Hospital in Boston, who has a sister with the condition.
In 2004, Stanford University neurobiologist Craig Garner and a student of his at the time, Fabian Fernandez, realized scientists might be able to counteract the Down Syndrome with drugs…
Researchers did a test in mice using an old GABA-blocking drug called PTZ. After 17 days, the treatment normalized the rodents’ performance on mazes and certain object recognition and memory tasks for as long as two months, according to results published in 2007 in Nature Neuroscience….
“It was bloody amazing,” Garner said by telephone. “It was shocking how well it worked.”
In their work, Hernandez, who is at Roche AG, and colleagues both at Roche and in academia chronically treated mice that have an animal version of Down syndrome with RO4938581, a drug that targets GABA receptors containing an alpha5 subunit. GABA is the major inhibitory transmitter in the brain, and in Down syndrome, there appears to be too much inhibitory signaling in the hippocampus – where, it so happens, GABA receptors with the alpha5 subunit are concentrated.
Treatment with RO4938581 improved the animals' memory abilities in a maze, decreased hyperactivity and reversed their long-term potentiation deficit. In the hippocampus, which is an important brain structure for memory and cognition, it also increased the birth rate of neurons back to the levels seen in normal animals, and led to a decrease in the number of inhibitory connections between cells.
In short there are two methods being developed, both potentially applicable to some autism:-
METHOD 1. Dampen GABAA receptors with an antagonist
METHOD 2. Dampen GABA with an inverse agonist of α5 sub-unit
Initially it was thought method 1 could not be used because of the risk of seizure/epilepsy.
“these drugs (GABAA antagonists) are convulsant at high doses, precluding their use as cognition enhancers in humans, particularly considering that DS patients are more prone to convulsions”
From:-
However this seems to have been overly conservative.
In the 2007 Stanford study they make a big point of their dosing being far lower than that used to induce seizures.
While you may need for a decade to get hold of Basmisanil (method 2), Cardiazol/PZT (method 1) is available in some pharmacies today. The only complication is that it is in a cough medicine that also contains Dihydrocodeine.
In some countries Dihydrocodeine is used in OTC painkillers along with paracetamol or ibuprofen, while in other countries it is a banned substance.
In Italy and India Cardiazol, with Dihydrocodeine, is given to toddlers as a cough medicine.
METHOD 1. Dampen GABAA receptors with an antagonist
As seems to be the case quite often, you can sometimes repurpose an old drug rather than spend decades developing a new one. This is the case with Cardiazol/ Pentylenetetrazol that was used in the Stanford trial.
Confusing Medical Jargon, (again)
Cardiazol, the name an elderly psychiatrist would recognize, is also called:-
· Pentylenetetrazol
· Pentylenetetrazole
· Metrazol
· Pentetrazol
· Pentamethylenetetrazol
· PTZ
· BTD-001
· DS-102
Other than to confuse us, why do they need so many names for the same drug?
Cardiazol/ Pentylenetetrazol is a drug that was widely used in the 1930s in Mental Hospitals to trigger seizures that were supposed to treat people with Schizophrenia. At much lower doses, it found a new purpose decades ago as an ingredient in cough medicine.
For a background into Cardiazol as a schizophrenia therapy, the following is not very pleasant reading:-
The 2007 Stanford trial of Cardiazol (there called PTZ) also trialed another GABAA antagonist called picrotoxin (PTX). Picrotoxin is, not surprisingly, a toxin, it is therefore a research drug but it has been given to horses to make them run faster.
Recent neuroanatomical and electrophysiological findings from a
mouse model of Down syndrome (DS), Ts65Dn, suggest that there is
excessive inhibition in the dentate gyrus, a brain region important for
learning and memory. This circuit abnormality is predicted to compromise normal mechanisms of synaptic plasticity, and perhaps mnemonic processing. Here, we show that chronic systemic administration of noncompetitive GABAA antagonists, at non – epileptic doses, leads to a persistent, post drug, recovery of cognition in Ts65Dn mice, as well as recovery of deficits in long – term potentiation (LTP). These data suggest that excessive GABAergic inhibition of specific brain circuits is a potential cause of mental retardation in DS, and that GABAA antagonists may be useful therapeutic tools to facilitate functional changes that can ameliorate cognitive impairment in children and young adults with the disorder.
One important things is that this cognitive enhancing effect persisted for a couple of months.
As you will see in the human clinical trial at the end of this post, they are comparing single doses with daily doses to understand the pharmokinetics.
The lead author, Craig Garner went on to start his own company because nobody seemed interested in his findings.
“Balance is now testing a GABA-blocking drug, BTD-001, on 90 adolescents and adults with Down syndrome in Australia, with results expected by early next year, said Lien, chief executive officer of the company.”
GABAA agonists and antagonists
The jargon does get confusing, if you want to stimulate GABAA receptors, you would use an agonist like GABA itself, or something that mimics it.
If you want to damp down the effect of GABAA receptors you would need an antagonist.
So if GABAA receptors are “malfunctioning”, you could either fix the malfunction or turn them down to reduce their effect.
If you cannot entirely repair the malfunction you could always do both. The overall effect might be better, or might not be, and it might well vary from person to person depending on the degree and nature of malfunction.
We saw in a previous post the idea of using drugs like bumetanide, diamox, and potassium bromide to restore E/I balance and then give GABA a little boost with a GABA agonist like Picamillon. This is very easy to test. In our case that little boost, did not help.
In those people who do not respond well, we can take the idea developed by Stanford for Down Syndrome and do the opposite, use a tiny amount of an antagonist, to see if that fine tuning has any beneficial effect. We now see this is both simple and safe.
METHOD 2. Inverse agonists of α5 sub-unit GABAA
I do like method 2, but would prefer not to wait another decade.
Method 2 sets out to improve cognitive function by dampening the activity of α5 sub-unit GABAA.
The Downs Syndrome researchers at Roche are developing Basmisanil/RG-1662 for this purpose. It will be a long while till it appears on the shelf of your local pharmacy.
I did look to see if there any clever ways to down regulate the α5 sub-unit of GABAA , other than those drugs being developed for Down Syndrome.
Inverse agonists of of α5 sub-unit GABAA
Pipofezine looks interesting.
Now we can compare Pipofezine with Mirtazapine. They are both this tricyclic antidepressants, so both closely related to H1 antihistamine drugs. We saw in earlier posts that Mirtazapine helps some people with autism in quite unexpected ways.
To be classed as a Pyridazines there has to be the benzene ring with two adjacent nitrogen atoms
So mirtazapine is not quite a Pyridazine, so may not directly affect the α5 sub-unit; but it does have potent effects elsewhere on the same receptor. It is will increase the concentration of neuroactive steroids that act as positive allosteric modulators via the steroid binding site on GABAA receptors.
We saw this in earlier posts that changes in progesterone levels affect not only the function of GABAA but even the subunit composition and hence indirectly possibly α5 sub-unit expression.
I previously suggested both progesterone and pregnenalone as potential autism therapies. Pregnenalone has since been trialed at Stanford.
The problem with these substances is that they are also female hormones and giving them in high doses to young boys is not a good idea. Stanford used adults in their trial.
However, affecting the metabolites of progesterone rather than increasing the amount of progesterone itself may give the good, without the bad. Also, perhaps there is a reason, oxidative stress perhaps, why progesterone metabolism might be disturbed in autism?
Anyway, it is yet another plausible reason why mirtazapine helps some people with autism.
Certain 3
-reduced metabolites of progesterone such as 3,5-tetrahydroprogesterone (3,5-THP, 5-pregnan-3-ol-20-one, allopregnanolone) and 3,5
-tetrahydroprogesterone (3,5-THP, 5-pregnan-3-ol-20-one, pregnanolone) are potent positive allosteric modulators of the 
-aminobutyric acidA (GABAA) receptor complex.1, 2, 3
Mirtazapine affects neuroactive steroid composition similarly as do SSRIs. The inhibition of the oxidative pathway catalyzed by the microsomal 3-HSD is compatible with an enhanced formation of 3-reduced neuroactive steroids. However, the changes in neuroactive steroid concentrations more likely reflect direct pharmacological effects of this antidepressant rather than clinical improvement in general.
So there may indeed be an effect on α5 sub-unit GABAA, but there is also an effect on another α5 subunit, this time the nicotinic acetylcholine receptors (nAChR). Those I looked at in earlier posts. This is getting rather off-topic.
The gene that encode the α5 sub-unit of nAChR is called CHRNA5. It is associated with nicotine dependence (and hence lung cancer), but is also linked to anxiety. GABA sub-units expression also plays a key role in anxiety. So a reason Mirtazapine should help reduce anxiety.
Pharmokinetics of Cardiazol
Since mouse experiments indicated an effect that continues after stopping using the drug, the clinical trials are particularly looking at the so called pharmokinetics. What is best a small daily dose or occasional larger doses?
You would hope they will be keeping a watchful eye on seizures.
I do not know what doses was used in those mental hospitals in the 1930s, but it must be well documented somewhere.
Experimental doses in adults vary widely from a “one off” 100mg to a daily dose of 2000mg. Look how they treat the 7 cohorts in the trial.
The cough medicine has 100mg of Cardiazol per 1ml
The usual dose is one drop per year of age, so a 12 year old would have a 0.6ml dose containing 60mg of Cardiazol. That is dosage is give 2 to 4 times a day, so up to 240mg a day
This dose is well up there with the dosage used in the above clinical trial, which starts at a one off dose of just 100mg or daily doses of 500mg in adults.
The above trial has been completed but the results have not been published.
If the trial is positive at the lower dose range, the cough medicine is a very cheap alternative.
Conclusion
I wish a safe inverse agonist of the α5 sub-unit of GABAA existed for use today.
I do not know anyone with Down Syndrome and this blog does not have many readers from Italy. The standard pediatric dose of Cardiazol Paracodina cough medicine might be well worth a try for both those with Down Syndrome and some autism with cognitive dysfunction.
We actual have quite a few readers from India and that is the only other country using this drug. In India the producer is Nicholas Piramal and the brand name is Cardiazol Dicodid, it cost 30 US cents for 10ml. So for less than $1, or 70 rupees, you might have a few months of cognitive enhancement, that is less than some people pay for 1 minute of ABA therapy.
If a few drops of this children’s cough medicine improves cognition please lets us all know.
