“More GABA” for Autism and Epilepsy? Not so Simple

Today’s post was prompted by Tyler highlighting a very recent paper from MIT and Harvard, with some interesting research on GABA in autism.  It also provides the occasion to include an interesting epilepsy therapy, which I encountered a while back.  This fits with my suggestion that the onset of much epilepsy in autism could be prevented.

In the MIT/Harvard study, they were looking into the excitatory/ inhibitory (E/I) imbalance found in ASD and schizophrenia. They used a non-invasive optical method to measure E/I imbalance and this did get some media coverage.  However, I am not sure this could be a diagnostic tool in very young children with classic autism, as was suggested; most such children would not cooperate.  It is not just a problem of being non-verbal, as was suggested in the media.

Indeed, due to the nature of the experiment, the researchers involved older subjects, with milder autism and none had MR/ID (IQ<70).  Being a trial done in the US, of the 20 autistic subjects, 11  were being treated with psychiatric medications: antidepressants (n = 8), antipsychotics (n = 2), antiepileptics (n = 4), and anxiolytics (n = 2).

The easy to read version is from the MIT website:-

Study finds altered brain chemistry in people with autism

The full version is here:-

Reduced GABAergic action in the Autistic Brain

They used something called Binocular Rivalry  as a proxy for  E/I imbalance.

During binocular rivalry, two images, one presented to each eye, vie for perceptual dominance as neuronal populations that are selective for each eye’s input suppress each other in alternation [16, 17]. The strength of perceptual suppression during rivalry is thought to depend on the balance of inhibitory and excitatory cortical dynamics [12–15] and may serve as a non-invasive perceptual marker of the putative perturbation in inhibitory signaling thought to characterize the autistic brain.

We therefore measured the dynamics of binocular rivalry in individuals with and without a diagnosis of autism (41 individuals, 20 with autism). As predicted, individuals with autism demonstrated a slower rate of binocular rivalry (switches per trial: controls = 8.68, autism = 4.19; F(1,37) = 16.52, hp 2 = 0.311, p = 0.001; Figure 1A), which was marked by reduced periods of perceptual suppression (proportion of each trial spent viewing a dominant percept, (dominant percept durations)/(dominant + mixed percept durations): controls = 0.69; autism = 0.55; F(1,36) = 7.27, hp 2 = 0.172, p = 0.011; Figure 1B). The strength of perceptual suppression inversely predicted clinical measures of autistic symptomatology (Autism Diagnostic Observation Schedule [ADOS]: Rs = 0.39, p = 0.027; Figure 1) and showed high test-retest reliability in a control experiment (R = 0.94, p < 0.001; see Supplemental Experimental Procedures and also [18]). These results replicate our previous findings in an independent sample of autistic individuals [11] and confirm rivalry disruptions as a robust behavioral marker of autism.

To test whether altered binocular rivalry dynamics in autism are linked to the reduced action of inhibitory (g-aminobutyric acid [GABA]) or excitatory (glutamate [Glx]) neurotransmitters in the brain, we measured the concentration of these neurotransmitters in visual cortex using magnetic resonance spectroscopy (MRS).

GABA and glutamate are predicted to contribute to different aspects of binocular rivalry dynamics: mutual inhibition between (GABA) and recurrent excitation within (glutamate) populations of neurons coding for the two oscillating percepts [14].

. Critically, reducing either mutual inhibition or recurrent excitation is predicted to reduce the strength of perceptual suppression during rivalry in one implementation of this model [14], mirroring the dynamics we observed in autism. We therefore considered each neurotransmitter separately to test whether inhibitory or excitatory signaling was selectively disrupted in the autistic brain.

As predicted by models of binocular rivalry, GABA concentrations in visual cortex strongly predicted rivalry dynamics in controls, where more GABA corresponded to longer periods of perceptual suppression (Rs = 0.62, p = 0.002; Figure 2B). However, this relationship was strikingly absent in individuals with autism (Rs = 0.02, p = 0.473; Figure 2B). The difference between the two correlations was significant (hp 2 = 0.167, p = 0.013; Figure 2C), indicating a reduced impact of GABA on perceptual suppression in the autistic brain.

GABA was working backwards

Importantly, this finding was specific to GABA: glutamate strongly predicted the dynamics of binocular rivalry in autism (Rs = 0.60, p = 0.004; Figure 2B), to the same degree as that found in controls.

Glumate is working just fine.

These findings suggest that alterations in the GABAergic signaling pathway may characterize autistic neurobiology. Consistent with prior evidence from animal and post-mortem studies, such dysfunction may arise from perturbations in key components of the GABAergic pathway beyond GABA levels, such as receptors [3–9] and inhibitory neuronal density

Together with the pivotal roles of GABA in canonical cortical computations [39] and neurodevelopment [40], these findings point to the GABAergic signaling pathway as a prime suspect in the neurobiology of this pervasive developmental disorder [41]

This study reconfirms what regular readers of this blog already knew.

Epilepsy

I thought it was positive that the MIT researchers suggested that the high level of epilepsy in autism and this E/I imbalance really must be connected.

I have been suggesting for some time that by correcting this E/I imbalance in children with autism, it is likely that the onset of epilepsy could be avoided (in some cases).

I did suggest this to one well known researcher who thought the idea of preventing the onset of epilepsy was not something that the medical community would accept as a concept.

I also raised the novel epilepsy therapy, below, to the same researcher who thought it also would never be considered.

The therapy was to use both bumetanide and potassium bromide to switch GABA back to inhibitory and then give a little boost using a GABA agonist.   

There are many types of epilepsy and some do not respond well to current treatments.  It would seem plausible that the autism-associated type of epilepsy might constitute a specific sub-type.

Combined effect of bumetanide, bromide, and GABAergic agonists: An alternative treatment for intractable seizures

Potassium Bromide was the original epilepsy therapy over a hundred years ago.  It is still used in Germany as a therapy.  Reports from a century ago suggest it has the same effect in autism as Bumetanide. (we saw this in my post on autism history). 

As you can see on Wikipedia there is a wide range of GABA agonists, but the only ones that would help in epilepsy and autism would be the ones that can cross the blood brain barrier.

GABA_A receptor Agonists

·         Bamaluzole

·         GABA

·         Gabamide

·         GABOB

·         Gaboxadol

·         Ibotenic acid

·         Isoguvacine

·         Isonipecotic acid

·         Muscimol

·         Phenibut

·         Picamilon

·         Progabide

·         Quisqualamine

·         SL 75102

·         Thiomuscimol

In an earlier post, we looked at the possible use of small doses of AEDs (anti-epileptic drugs).  One reader found that tiny dose of Valproate (known to raise GABA) had a positive effect when combines with Bumetanide.

In a recent comment one reader showed the same result by combing picamilon with bumetanide.

Both Picamilon and Valproate are having the effect proposed by the epilepsy researchers.

Potassium Bromide does have known side effects, but the idea of further boosting the effect of Bumetanide is interesting.  I have suggested before that this should also be possible using Diamox (Acetazolamide).  Diamox does not affect NKCC1 or E_GABA,  it affects the  Cl-/HCO3-exchanger AE3  to further affect Cl- levels.  

I did suggest this a long time ago in my posts on the GABAa receptor.  I am not the only one to realize this.

NKCC1 and AE3 Appear to Accumulate Chloride in Embryonic Motoneurons

   

Picamilon is well researched Russian drug, sold in other countries as a supplement.  It is a modified version of GABA that includes niacin; together it can cross the blood brain barrier (BBB).

So I think a better version of what the epilepsy researchers suggest might be:-

                           Bumetanide  +  Diamox  +  a touch of Picamilon

What would be the effect in autism?

Treatment of Autism with low-dose Phenytoin, yet another AED

I do like coincidences and I do like not struggling to find a picture for my posts. 

Phenytoin (Dilantin) is a drug that appeared in the novel and film, One Flew Over the Cuckoo's Nest, but then it was not used in low-doses.

Today’s post follows from a comment I received about using very low doses of anti-epileptic drugs (AEDs) in autism.

First of all a quick recap.

Clonazepam was discovered by Professor Catterall, over in Seattle, to have the effect of modifying the action of the neurotransmitter GABA to make it inhibitory, at tiny doses that would be considered to be sub-clinical (i.e. ineffective).

Valproate, another AED, was discovered by one of this blog’s readers also to have an “anti-autism” effect in tiny doses of 1 mg/kg.

A psychiatrist from Australia, Dr Bird, specialized in adults with ADHD has just published a paper about the benefit of low-dose phenytoin in adult autism.  The same psychiatrist has also earlier encountered the effect of low dose valproate in ADHD (autism lite).

The treatment of autism with low-dose phenytoin: a case report

Significantly, this beneficial effect of sodium valproate appeared to have a narrow therapeutic window, with the optimal range between 50 and 200mg daily. A complete loss of efficacy frequently occurred above a dose of 400mg.

Case presentation

My patient was a 19-year-old man diagnosed in early childhood with ADHD and ASD

a sublingual test dose of approximately 2mg phenytoin was administered

Within 10 minutes of taking the sublingual phenytoin he reported a reduction in the effort required to contribute to conversation and was able to sustain eye contact both when listening and speaking. He was surprised about the effortless nature of his eye gaze and also commented that he had never done this before.

The following day he started taking compounded 2mg phenytoin capsules in the morning in conjunction with his methylphenidate.

After two weeks both he and his mother stated that his communication with the family had improved and there had been no aggressive outbursts.

Over the next four weeks he became inconsistent in taking the phenytoin, and then ceased altogether. His behavior reverted to the previous pattern of poor social interaction; he became oppositional with outbursts of anger and physical violence.

Nine months later he resumed taking the phenytoin, this time as a single 4mg capsule in the morning. After his first dose there was an improvement of his social behavior similar to his previous response, although there was an apparent deterioration in the late afternoon. The dose was increased from 4mg to 5mg and a larger capsule formulated to try and prolong the release of the phenytoin. This appeared to achieve a more consistent improvement in behavior throughout the day, evident both at home and at work. Increases in the dose above 5mg were not associated with any additional benefit. He remained on the 5mg dose of phenytoin for over 18 months and reported that his work performance had consistently improved sufficient to increase his working hours and his level of responsibility. The violence and destruction at home abated. His confidence improved and for the first time he has established and sustained peer-appropriate friendships.

I hypothesize that, in a similar mechanism to the low-dose clonazepam in this animal model of autism, low-dose phenytoin may enhance GABA neurotransmission, thereby correcting the imbalance between the GABAergic and glutaminergic systems.

Phenytoin

Now let us look at Phenytoin and see if we agree with Dr Bird's hypothesis that the mechanism is the same as low dose clonazepam. 

The accepted method of action is that working as a voltage gate sodium channel blocker.  GABA is not mentioned.

Phenytoin, by acting on the intracellular part of the voltage-dependent sodium channels, decreases the sodium influx into neurons and thus decreases excitability.

The antiepileptic activity of phenytoin was found during systematic research in animals: it suppresses the tonic phase but not the clonic phase elicited by an electric discharge and is not very active against the attacks caused by pentylenetetrazol.

Phenytoin was the first non-sedative antiepileptic to be used in therapeutics.

It decreases the intensity of facial neuralgia and has an antiarrhythmic effect.

 But as I dug a little deeper, I found from 1995:-

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

 Abstract

We report here that carbamazepine and phenytoin, two widely used antiepileptic drugs, potentiate gamma-aminobutyric acid (GABA)-induced Cl- currents in human embryonic kidney cells transiently expressing the alpha 1 beta 2 gamma 2 subtype of the GABAA receptor and in cultured rat cortical neurons. In cortical neuron recordings, the current induced by 1 microM GABA was enhanced by carbamazepine and phenytoin with EC50 values of 24.5 nM and 19.6 nM and maximal potentiations of 45.6% and 90%, respectively. The potentiation by these compounds was dependent upon the concentration of GABA, suggesting an allosteric modulation of the receptor, but was not antagonized by the benzodiazepine (omega) modulatory site antagonist flumazenil. Carbamazepine and phenytoin did not modify GABA-induced currents in human embryonic kidney cells transiently expressing binary alpha 1 beta 2 recombinant GABAA receptors. The alpha 1 beta 2 recombinant is known to possess functional barbiturate, steroid, and picrotoxin sites, indicating that these sites are not involved in the modulatory effects of carbamazepine and phenytoin. When tested in cells containing recombinant alpha 1 beta 2 gamma 2, alpha 3 beta 2 gamma 2, or alpha 5 beta 2 gamma 2 GABAA receptors, carbamazepine and phenytoin potentiated the GABA-induced current only in those cells expressing the alpha 1 beta 2 gamma 2 receptor subtype. This indicates that the nature of the alpha subunit isoform plays a critical role in determining the carbamazepine/phenytoin pharmacophore. Our results therefore illustrate the existence of one or more new allosteric regulatory sites for carbamazepine and phenytoin on the GABAA receptor. These sites could be implicated in the known anticonvulsant properties of these drugs and thus may offer new targets in the search for novel antiepileptic drugs.

So not only is it possible that phenytoin can modulate the behaviour of the GABA_A receptor like Dr Catterall did with Clonazepam, but carbamazepine is yet another known AED with this effect.

So I expect someone will also go and patent low-dose carbamazepine for autism.

We potentially now have a wide range of low dose AEDs for autism.

·        Valproate (1000 to 2000 mg for adults as AED) at a dose of 1-2 mg/kg

·        Clonazepam (up to 20 mg for adults as an AED)   at a dose of 1.7mcg/kg

·        Phenytoin (up to 600 mg for adults as an AED) at a dose of 0.05 mg/kg

·        Carbamazepine (up to 1,200 mg for adults as an AED) no data for the low dose!

We also have two other drugs that are used as AEDs in high doses and have been used in autism with much lower doses.  I do not have any evidence to show that they affect GABA_A receptors.  I think their method of action is unrelated to GABA, or sodium channels.

  

·        Piracetam (up to 24 g as an AED) at a dose of 400 to 800 mg

·        Vinpocetine (up to 45mg for adults as an AED)  at a dose of 1 to 5 mg

Both Piracetam and Vinpocetine are classed as drugs in Europe and supplements in the US.  Both are also used as cognitive enhancers. Both have numerous possible modes of action.  They may not help with behavioral problems, but may well improve cognition.

Interestingly, a clinical trial is underway to look at the cognitive effect of moderate doses of Vinpocetine in epilepsy.

Cognitive Effects of Vinpocetine in Healthy Adults and Patients With Epilepsy

Modified Use of Anti-Epileptic Drugs (AEDs) at Low Doses in Autism

As readers will be aware, many people with more severe autism are also affected by epilepsy.  Siblings of those with autism also seem to be at greater risk of epilepsy.

There are frequent comments that once starting on AEDs (Anti-Epileptic Drugs) aspects of autism also seem to improve.  This should not be surprising given the suggested action of these drugs and the overlapping causes of epilepsy and autism.

Today’s post is prompted by the observation that in very low, apparently sub-therapeutic, doses some AEDs seem to improve autism in some cases.  This is relevant because the usual high doses of these drugs are associated with some side effects and indeed a small number can be habit forming.

What is epilepsy?

The cause of most cases of epilepsy is unknown.

Genetics is believed to be involved in the majority of cases, either directly or indirectly. Some epilepsies are due to a single gene defect (1–2%); most are due to the interaction of multiple genes and environmental factors.  Each of the single gene defects is rare, with more than 200 in all described.  Most genes involved affect ion channels, either directly or indirectly. These include genes for ion channels themselves, enzymes, GABA, and G protein-coupled receptors.

Much of the above applies equally to autism, including the genetic dysfunctions associated with GABA.  The ion channel dysfunctions in epilepsy are thought to be mainly sodium channels, like Nav1.1.  We previously came across this channel when looking at Dravet Syndrome.

Dravet Syndrome

Dravet Syndrome is rare form of epilepsy, but is highly comorbid with autism.  It is cause by dysfunctions of the SCN1A gene, which encodes the sodium ion channel Nav1.1.  There is a mouse model of this condition, used in autism research.  Dravet Syndrome is known to cause a down-regulation of GABA (the neurotransmitter) signaling.  We saw how tiny doses of Clonazepam corrected this dysfunction in mice.

Known ASD-associated mutations occur in the genes CACNA1C, CACNA1F, CACNA1G, and CACNA1H, which encode the L-type calcium channels Cav1.2 and Cav1.4 and the T-type calcium channels Cav3.1 and Cav3.2, respectively; the sodium channel genes SCN1A and SCN2A, which encode the channels Nav1.1 and Nav1.2, respectively; and the potassium channel genes KCNMA1 and KCNJ10, which encode the channels BKCa and Kir4.1, respectively.

Channelopathies in Autism - Treating Nav1.1 with Clonazepam

Dr Catterall, the researcher, then went on to test low dose clonazepam in a different mouse of autism model and found it equally effective.  It also appears to work in some human forms of autism.

Sodium Valproate

Valproate is a long established epilepsy drug that has also been used widely as a mood stabilizer and particularly to treat Bipolar Disorder.

One side effect can be hair loss.  Hair loss/growth and also hair greying are frequently connected with drugs and genes linked to autism (BCL-2, biotin, TRH etc).

One regular reader of this blog has pointed out that a tiny dose of Valproate, when combined with Bumetanide, appeared to have a significant and positive effect.  We know that bumetanide works via NKCC1 and the GABA_A receptor to make GABA more inhibitory.

Many modes of action are proposed for Valproate, but the most mentioned one is that it increases GABA “turnover”; so it would make sense that having shifted the balance from excitatory to inhibitory, a stimulation to increase GABA signaling might be beneficial.

What is odd is that this is happening at a dose 20 times less than used in epilepsy, bipolar or mood disorders.

The use of Clonazepam, discovered by Dr Catterall, is also at a dose 20 to 50 times less than the typical dose.

Clonazepam and Valproate are both AEDs.  There are not so many of these drugs and while using them at high doses, without dire need, might be highly questionable, their potential effectiveness at tiny doses is very interesting.

Clonazepam is a Benzodiazepine in the table below.

The above table is from the following paper:-

 Mechanisms of action of antiepileptic drugs

Low Dose Clonazepam

Low dose Clonazepam was shown to be effective by its action of modulating the GABA_A receptor to make it more inhibitory.  There are different types of GABA_A receptor and the low dose effect was sub-unit specific.  Other benzodiazepine drugs were found to have the opposite effect.

The mouse research showed that the effect only appeared with a narrow range of low dosages.

Low Dose Valproate

Valproate is known to affect sodium channels like Nav1.1, but also some calcium channels.

For an insight into some known potential effects of Valproate, here is a paper from the US National Institute of Mental Health:-

Therapeutic Potential of MoodStabilizers Lithium and Valproic Acid: Beyond Bipolar Disorder

In the paper it highlights the less well known effects of Valproate:-

inhibits HDACs

Modulates Neurotrophic and Angiogenic Factors (BDNF, GDNF, VEGF)

PI3K/Akt Pathway

Wnt/β-Catenin Pathway

MEK/ERK Pathway

Oxidative Stress Pathways

Enhanced Neuroprotection

Enhancing the Homing and Migratory Capacity of Stem Cells

Here is a list of the suggested new applications of Valproate, many highly appropriate to many types of autism:-

       Repurposing Mood Stabilizers for CNS Disorders Beyond BD

       A. Stroke

       1. Lithium-Induced Effects in Experimental Stroke Models

       a. Neuroprotection and behavioral improvement

       b. Anti-excitotoxic and anti-apoptotic effects

       c. Anti-inflammation

       d. Angiogenesis

       e. Neurogenesis

       f. Effects on MSC migration after transplantation

       2. VPA-Induced Effects in Experimental Stroke Models

       a. Neuroprotective effects and behavioral benefits

       b. Anti-inflammation

       c. BBB protection

       d. Angiogenesis

       e. Neurogenesis

       B. TBI

       1. Lithium-Induced Effects on Neurodegeneration, Neuroinflammation, Behavioral Improvement, and Aβ Accumulation in Models of TBI

       2. VPA-Induced Effects on Neurodegeneration, Neuroinflammation, and Functional Recovery in Models of TBI

       3. Clinical Trials of VPA Treatment in TBI

Having read that paper I am now not surprised that a tiny dose of valproate can have a positive behavioral effect in autism.  What would be interesting to know is how the effects and dominant modes of action vary with dosage.  I presume the dosage has been optimized to control/prevent seizures.

Valproate is a cheap drug and is available as a liquid, so accurate low dosing is possible.  It has been shown to be neuro-protective, even shown promise as a treatment for traumatic brain injury.

While not written about autism, some of you may find the following collection of research interesting:-

Brain Protection in Schizophrenia, Mood and Cognitive Disorders

It does talk about the wider potential use of Valproate, but not at tiny doses.

Stiripentol

Interestingly, an orphan drug was developed in the European Union to treat Dravet Syndrome.  It is included on the list of AEDs above.

Even though that drug, Stiripentol, is not approved by the FDA, most sufferers in the US are able to acquire it under the FDA’s Personal Importation Policy(PIP).

So it is indeed possible to acquire drugs prior to approval in your home country.

Hopefully, once Bumetanide is approved for autism in Europe, similarly people will be able to access it easily in the US.

I wonder if anybody with Dravet Syndrome has tried low dose Clonazepam.  In theory it should be helpful.