Psilocybin, autism and depression: the psychedelic experience is apparently not needed

 

I like today’s post because it draws together some reader experience, autism research from the 1960s, with modern day lab research and human trials.

A distinct subgroup of our readers fall into what is today level 1 autism, which many think was better described as Asperger’s. Even though cognition and language are not impaired, some can have severe struggles, including anxiety, depression and feeling they do not quite fit in. Remarkably, in some cases just getting an official diagnosis provides a boost, “it's not me, it's my autism”. If that is sufficient therapy, then great.

For the Aspies seeking a better life, some end up looking at their serotonin receptors.

I recently wrote a review of all of them, but the Aspie focus tends to be 5-HT2A.

Rethinking the role of serotonin receptor signaling in improving autism symptoms: Prucalopride for a sub-group?

Incidentally, the mother who prompted that post tells me that her adult son continues to show the behavioral benefit from prucalopride one month later.

5-HT2A was the target of Ivar Lovaas back in 1966 at UCLA in Los Angeles. Lovaas is best known today for his work in Applied Behavioral Analysis (ABA).

Back in 1966 he published this paper:

Modificationof autistic behavior with LSD-25

The study involved a pair of identical autistic twin boys, then around five years old.

The researchers were interested in whether LSD could modify behaviours that were particularly difficult to change in severely affected children.

 

Our reader comments

One of the most notable comments in this blog was written by an Aspie who found a single experience with stimulating 5-HT2A provided a lasting beneficial shift in his mood.

You might wonder how such an effect could occur, like flipping a switch.

The recent research now explains why this likley happened.

 

The 1966 LSD study was tiny and exploratory by modern standards. It cannot establish that LSD was an effective treatment for autism, and the behavioural changes reported were principally observed during the drug sessions. It is therefore important not to read modern ideas about long-lasting psychedelic effects back into the 1966 experiment.

Nevertheless, the study is historically remarkable.

Lovaas was involved in research asking whether altering brain function could alter autistic behaviour.

Then the science took a different path.

 

60 years later we are back to psilocybin – depression in humans, autism in mice

A new study has taken the question into a modern genetic model of autism.

The researchers used mice lacking Cntnap2, a gene associated with neurodevelopmental disorders in humans. These mice show reduced sociability together with hyperactivity and repetitive behaviour.

A single dose of psilocybin produced a persistent increase in social behaviour.

The effect was detectable one day later and remained for at least two weeks. Importantly, the mice did not simply become more active: their overall exploration and locomotion did not show the same change.

And psilocybin did not correct everything.

The hyperactivity and repetitive grooming remained elevated.

This is therefore not evidence that psilocybin "reverses autism."

It is evidence that a brief pharmacological intervention can produce a persistent change in one particular behavioural phenotype in a particular genetic mouse model.

There was another important finding.

The same treatment did not increase sociability in genetically normal control mice.

That suggests something much more interesting than a simple "socialising" effect.

Perhaps the drug is interacting with an abnormal neural state.

 

The 5-HT2A receptor

Psilocybin's psychedelic effects are primarily mediated through the serotonin 5-HT2A receptor.

The researchers blocked this receptor before administering psilocybin.

The persistent improvement in sociability disappeared.

This gives us an important mechanistic sequence:

 

Psilocybin

↓

5-HT2A activation

↓

persistent biological change

↓

altered social behaviour

 

But then came the most surprising experiment.

The mice did not have to experience the psychedelic state

The researchers administered psilocybin while the mice were under light anaesthesia.

The animals therefore experienced the acute pharmacological action of psilocybin while unconscious.

When tested later while awake, they showed the same persistent increase in sociability.

In other words, an awake psychedelic experience was not required for the lasting behavioural effect in these mice.

The psychedelic experience is not itself the fundamental therapeutic mechanism.

It is one consequence of activating 5-HT2A receptors, while another consequence is a longer-lasting biological change in the brain.

 

What could produce a lasting effect?

One possibility is that the brief receptor signal initiates a cascade of molecular and cellular changes.

There is increasing evidence from psychedelic research that psilocybin can influence gene expression, neuronal structure, synaptic organisation and brain network function.

Epigenetic mechanisms may also be involved.

In the Cntnap2 work, the researchers found evidence that DNA-methylation machinery is required for the persistent behavioural effect. 

Researchers found that blocking DNMT1, a key DNA-methylation enzyme, prevented this persistent effect.

Importantly, DNMT1 inhibition did not prevent the acute 5-HT2A-related response.

This suggests DNA-methylation machinery acts downstream of 5-HT2A activation to maintain the longer-term change.

The finding points to a molecular mechanism whereby a brief drug exposure can produce behavioural effects long after the psychedelic experience has ended.

This suggests that a short-lived pharmacological signal may be converted into a longer-lasting change in gene regulation.

We do not yet know that psilocybin permanently rewrites the epigenome in these mice.

Nor do we know that the behavioural change is caused by a permanent epigenetic modification.

A more cautious model would be:

 

brief 5-HT2A stimulation

↓

intracellular signalling

↓

changes in gene regulation and possibly epigenetic state

↓

altered capacity for neural plasticity

↓

changes in neural circuits

↓

persistent change in behaviour

 

The important word is persistent, not permanent.

 

Could this matter for depression in autistic people?

This brings us back to humans.

Depression and persistent low mood occur in some autistic people, and this may be a particularly interesting population for psychedelic research.

Psilocybin has already produced persistent antidepressant effects in studies of people with major depressive disorder.

But there is an important unanswered question:

 

Would an autistic person with depression respond in the same way?

We do not yet know.

Autism is heterogeneous, and depression in an autistic person need not have exactly the same biological basis as depression in a non-autistic person.

Nevertheless, the new mouse findings make the question more interesting.

The drug did not simply increase sociability in every animal.

And now the experiment has returned to humans

The circle is becoming particularly interesting because researchers are now asking the same mechanistic question in humans.

A Stanford Phase 2 study, SPACE, is investigating psilocybin administered under general anaesthesia in people with major depressive disorder. The rationale is to suppress the noticeable psychological effects of psilocybin, making it possible to investigate whether effects can occur without the conscious psychedelic experience.

This is not an autism study, and it is small and experimental.

But scientifically it is fascinating.

Can separate the pharmacological action of psilocybin from the subjective psychedelic experience?

If lasting antidepressant effects were observed despite anaesthesia, that would provide important evidence that the biological action of 5-HT2A stimulation can produce therapeutic effects independently of the psychedelic experience.

 

From LSD in autistic humans to psilocybin in autistic mice and depressed humans

This brings us back to the historical arc.

1966 — UCLA

Lovaas and colleagues studied LSD in autistic children.

The question was whether changing brain function could modify autistic behaviour.

The following decades

Lovaas's research increasingly concentrated on behavioural intervention.

The question became whether changing the environment and learning experience could change behaviour and development.

2026 — autism mouse model

Researchers can now manipulate the biology much more precisely.

They can alter a specific autism-associated gene, activate 5-HT2A receptors, block the receptor, examine molecular pathways and administer the drug while the animal is unconscious.

And they find that a brief exposure to psilocybin can produce a behavioural effect that persists after the drug and the psychedelic state have disappeared.

2026 — depressed humans

Researchers are now taking the question back into humans.

Can psilocybin produce a lasting antidepressant effect without the person experiencing the psychedelic state?

The historical arc is therefore almost a circle.

 

Why did they choose the CNTNAP2 model and how this relates to Pitt Hopkins

The researchers did not choose the Cntnap2 mouse because it represents autism as a whole. They chose it because it is an established genetic model with a measurable reduction in sociability. Cntnap2-knockout mice show reduced social interaction, together with hyperactivity and repetitive behaviour. This gave the researchers a way to ask a very specific question: can psilocybin change an abnormal social phenotype?

The result was quite specific. Psilocybin increased the mice's preference for the social stimulus without significantly increasing their general exploration or movement. It also did not correct the hyperactivity or repetitive grooming.

The researchers also tested genetically normal mice. They did not show the same beneficial increase in sociability. This is important because it suggests that psilocybin may interact differently with a brain that already has an altered neurodevelopmental state, rather than simply acting as a general social enhancer.

 

Why is this relevant to Pitt Hopkins?

CNTNAP2 is particularly interesting in relation to Pitt Hopkins because biallelic CNTNAP2 mutations cause a Pitt-Hopkins-like neurodevelopmental disorder. Classical Pitt-Hopkins syndrome, however, is caused by alterations in TCF4.

There is also a biological relationship between the two genes. TCF4 is a transcription factor that can regulate CNTNAP2 expression. Thus, CNTNAP2 sits within a neuronal gene-regulatory network that is relevant to Pitt-Hopkins biology.

This does not mean that a Cntnap2-knockout mouse is a model of classical Pitt-Hopkins syndrome. The primary genetic abnormalities are different, and the findings cannot be directly extrapolated from Cntnap2 mice to people with Pitt Hopkins.

There is another important difference. Reduced social motivation is a clear phenotype of the Cntnap2 mouse, but it should not automatically be assumed to be the principal social problem in Pitt Hopkins syndrome.

People with Pitt Hopkins can have profound communication and social-communication difficulties, but many also actively seek attention, enjoy being with other people and show considerable social interest. In other words, the ability to communicate socially and the motivation to engage socially are not necessarily the same thing.

This means that if psilocybin were investigated in Pitt Hopkins, increasing social motivation would not necessarily be the most appropriate primary outcome.

Instead, researchers could ask whether it changes social communication, spontaneous communication, mood/affect, anxiety, repetitive behaviours, adaptive functioning or other measurable Pitt Hopkins phenotypes.

 

The research question

The Cntnap2 finding nevertheless raises an intriguing question for Pitt Hopkins:

If 5-HT2A activation can produce a persistent improvement in a behavioural phenotype caused by disruption of CNTNAP2, could it also modify some downstream consequences of TCF4 dysfunction?

The next logical experiment would therefore be to test psilocybin in a Tcf4 haploinsufficient Pitt Hopkins mouse model.

Researchers could examine not only behaviour but also the underlying biology:

• Does 5-HT2A activation alter the synaptic abnormalities associated with TCF4 deficiency?
• Does it affect gene expression or epigenetic regulation?
• Does it alter neuronal plasticity?
• Are any behavioural effects persistent after the drug has disappeared?
• Does the effect require the conscious psychedelic state, or could it occur under anaesthesia as in the Cntnap2 experiment?

The most interesting possibility would be a downstream compensation: the TCF4 mutation would remain, but a transient pharmacological intervention might alter some of the neuronal consequences of that mutation and allow the system to function differently.

 

Pitt-Hopkins is already being approached through epigenetics

There is an especially interesting parallel here because Pitt-Hopkins researchers are already testing an epigenetic strategy in humans. The RVL-001 trial, being conducted by Unravel Biosciences with the Pitt Hopkins Research Foundation in Colombia, is testing Vorinostat, a histone deacetylase (HDAC) inhibitor, in people with genetically confirmed Pitt Hopkins syndrome. The current exploratory study is small and is designed to examine safety and efficacy, as well as changes in the transcriptomic profile.

Vorinostat is approaching the problem from a very different direction than psilocybin. Rather than activating 5-HT2A receptors and potentially initiating downstream changes in neuronal signalling and plasticity, vorinostat directly alters epigenetic regulation by inhibiting HDAC enzymes, thereby changing how tightly DNA is packaged around histones and influencing gene expression.

There is a particularly strong rationale for this in Pitt Hopkins. In Tcf4-haploinsufficient mice, HDAC inhibition with vorinostat normalized abnormalities in hippocampal long-term potentiation and memory recall. Molecular studies also found changes in gene expression and DNA methylation associated with the treatment.

This creates an intriguing contrast:

Pitt-Hopkins genetic defect → TCF4 haploinsufficiency → abnormal gene regulation

Vorinostat: attacks the problem directly at the epigenetic/transcriptional level

versus

Psilocybin: 5-HT2A activation → intracellular signalling → potentially altered gene regulation/plasticity → possible downstream compensation.

 

In other words, these are two very different ways of trying to change the functional consequences of the same developmental genetic disorder.

The important point is that neither approach corrects the underlying TCF4 mutation. Both are attempting to modify downstream consequences of TCF4 deficiency.

 

Gene therapy

As was discussed in the recent post on gene therapy, there is now a fundamentally different approach being investigated in Pitt Hopkins: gene therapy.

Pitt Hopkins is caused by loss of function of one copy of TCF4, so gene therapy attempts to address the problem at its source. The investigational therapy MZ-1866 uses an AAV9 vector to deliver a functional copy of TCF4 to the brain.
It is being tested in a Phase 1/2 first-in-human clinical trial. The first participant was dosed in February 2026.
The current study is investigating safety and tolerability as well as potential clinical effects.
Unlike vorinostat or psilocybin, this approach is attempting to restore the missing genetic function itself.

Conclusion

Some Aspie readers of this blog have already established that a single dose of Psilocybin can produce long lasting improvements in social behavior. They skipped the mouse models and adopted the Nike approach.

The LSD trials in children in the 1960s assumed that the psychedelic experience was the therapy, now we see that this is not the case. You can sleep through it and still get the long lasting effect.

The beneficial effect in CNTNAP2 mice does indicate that the experiment should be repeated in the closely related Pitt Hopkins model. Of course, it should also be checked in idiopathic autism models like the BTBR and the maternal immune activation (MIA) model

In the prenatal valproate (VPA) model, psilocybin was previously tested and it did rescue the social-behavioural abnormalities. 

Note

Psilocybin is the main psychoactive compound found in “magic mushrooms.” It is converted in the body into psilocin, which produces the psychedelic effects. Research using purified psilocybin therefore studies the key active psychedelic component rather than the whole mushroom.

Ethosuximide to increase speech in some autism? and PTHS?

I have previously proposed the use of calcium T channel blockers to treat some types of autism. I did suggest that language might be a good target.

Time for T? Targeting language-associated gene Cntnap2 with a T-type calcium channel blocker corrects hyperexcitability driving sensory abnormalities, repetitive behaviors, and other ASD symptoms, but will it improve language? Will it also benefit Pitt Hopkins syndrome (PTHS) and broader autism?

I recently received a question from a reader who read an abstract from a paper presented to the Brain Foundation, that suggested Ethosuximide can increase speech in autism. She also asked what the effective dosage might be.

This subject has come up before in this blog. Ethosuximide is a very specific T channel blocker, commonly used to treat absence seizures. Some readers of this blog have already trialed it. The other interesting one is Zonisamide, which blocks T channels but also has other effects. We have reports that the starting low dose of Zonisamide had some interesting beneficial effects that were lost at the regular higher doses.

I did not expect to find much new information, but that changed when I found the patent document submitted by Charles Niesen. So here is a blog post dedicated to this specific subject.

Here is the full patent:

Method of treating expressive language deficit in autistic humans

Here is an easy-to-read summary:

 

A New Patent Claims an Unusual Approach to Autism Language Deficits

A recent patent proposes a novel pharmacological method for improving expressive language in individuals with autism. Rather than introducing a new drug, the invention repurposes a class of existing anticonvulsant medications—specifically succinimides such as ethosuximide, methsuximide, and phensuximide.

These drugs have long been used to treat epilepsy, particularly absence seizures. However, the patent suggests they may also address one of the most challenging aspects of autism: the inability to initiate and sustain meaningful verbal communication.

 

Understanding the Problem

Autism is often characterized by difficulties in social interaction, but a core feature—especially in more severe cases—is expressive language impairment. Many individuals with autism may speak only in short phrases or single words. Others may respond to questions but rarely initiate conversation or engage in back-and-forth dialogue.

This is distinct from related conditions like Asperger syndrome, where language is typically intact but social communication is impaired. In classic autism, the issue is not just how language is used—but whether it emerges spontaneously at all.

Currently, there are no FDA-approved medications specifically designed to improve expressive language in autism. Most available treatments focus on associated symptoms such as irritability, seizures, or attention deficits.

 

The Core Idea Behind the Patent

The patent proposes that daily administration of a succinimide anticonvulsant—most notably ethosuximide—over an extended period (typically several months) can significantly improve expressive language abilities.

Patients are treated for at least one month, with stronger effects reported after three to six months or longer. The goal is not just increased vocabulary, but a progression toward spontaneous speech and true conversational ability.

 

How Might This Work?

Ethosuximide works by blocking T-type calcium channels in the brain. These channels play a role in regulating neuronal activity and rhythmic signaling.

While the exact mechanism in autism is unknown, the patent speculates that modulating these channels may help normalize communication between brain regions involved in language. Another hypothesis is that the drug may “activate” previously underused or dormant neural circuits.

These ideas remain theoretical and are not yet confirmed by broader research.

 

Dosage and Treatment Approach

The proposed dosing follows standard epilepsy guidelines, typically ranging from 10 to 60 mg per kilogram of body weight per day. In many cases, a range of 20–40 mg/kg/day is used for children, while adolescents and adults may receive fixed doses between 150 mg and 1000 mg twice daily.

Treatment is administered consistently over months, with periodic evaluation of language and behavioral progress.

 

How Speech Was Measured

To evaluate improvement, the patent uses a simple but structured 7-point expressive language scale. This scale attempts to quantify how advanced a person’s spoken communication is, ranging from no speech at all to full conversational ability.

The scale is defined as follows:

• 0 — Nonverbal: No meaningful spoken language
• 1 — Echolalic: Repeats words or phrases (echoing others)
• 2 — Single words: Uses isolated words to communicate
• 3 — Phrases: Combines words into short phrases
• 4 — Sentences: Forms complete, understandable sentences
• 5 — Spontaneous speech: Initiates speech independently
• 6 — Mutual speech: Engages in true back-and-forth conversation

This scale is central to the patent’s claims. Improvements are measured as movement upward along these stages—for example, progressing from single words (2) to phrases (3), or from sentences (4) to spontaneous speech (5).

The inventors argue that even a 1–2 point increase represents a meaningful functional gain in real-world communication.

 

Summary of the Reported Study

The patent describes a small observational study involving 24 patients with autism. Participants were treated with ethosuximide for periods ranging from one month to over six months.

Patients were grouped based on cognitive level, including normal IQ, borderline, mild impairment, and moderate impairment. Language ability was assessed using the 7-point scale described above.

 

Reported Outcomes

Across all groups, improvements in expressive language were observed. The most significant gains occurred in individuals with higher baseline cognitive function.

On average, patients improved by approximately two points on the language scale. This often meant progressing from single words to phrases, or from phrases to full sentences and occasional spontaneous speech.

In some documented cases, children who initially spoke only in isolated words were able to form sentences within six months and engage in basic conversation within a year.

 

Timeline of Improvement

Initial changes were sometimes observed within the first month of treatment. More consistent and substantial gains were reported after three months, with the most pronounced improvements occurring after six months or longer.

Interestingly, the progression of language development in treated patients appeared to mirror typical early childhood language acquisition—albeit delayed.

 

Persistence After Treatment

One of the more striking claims is that improvements persisted even after the medication was discontinued. In several cases, language abilities continued to develop beyond the treatment period.

This suggests the possibility of longer-term changes in neural function, rather than temporary symptom management.

 

Additional Observations

Beyond language, some patients also showed improvements in social interaction and mood. Increased engagement, better eye contact, and reduced irritability were noted in certain cases.

However, many participants were also receiving speech therapy and applied behavioral analysis (ABA), making it difficult to isolate the effects of the medication alone.

 

Safety Profile

Ethosuximide was generally well tolerated in the study. Known side effects include gastrointestinal discomfort, fatigue, and behavioral changes. Rare but serious risks—such as blood or liver abnormalities—are also associated with the drug and require medical supervision.

 

Age Range and Cognitive Profile of Participants

The patent provides limited but useful information about the participants’ ages and cognitive abilities.

Age Range

• The study included both young children and adolescents.
• Specific examples mention children as young as 3 years old and others up to around 12–15 years old.

Cognitive (IQ) Groups

Participants were divided into four categories based on cognitive level:

• Normal IQ (NIQ)
• Borderline IQ (BIQ)
• Mild intellectual impairment (mMR)
• Moderate intellectual impairment (moMR)

 

Key Takeaways

• The strongest language improvements were reported in children with normal IQ.
• Children with lower cognitive levels also improved, but to a lesser degree.
• The results suggest that baseline cognitive ability may influence response to treatment.

 

Final Thoughts

This patent presents an intriguing hypothesis: that a well-established epilepsy medication may have the potential to improve core language deficits in autism.

The reported results are promising, particularly the magnitude of language gains and their persistence after treatment. However, the evidence is limited by the small sample size, lack of a control group, and reliance on a subjective rating scale.

As it stands, this work should be viewed as exploratory rather than definitive. Larger, controlled clinical trials would be needed to determine whether this approach truly offers a reliable and reproducible benefit.

Still, the idea highlights an important direction for future research—targeting the underlying neural mechanisms of communication itself, rather than just managing associated symptoms.

 

Critical periods and CNTNAP2

Another factor to consider is the role of developmental “critical periods,” when brain circuits involved in language are particularly plastic. Disruption of CNTNAP2 has been linked to altered neuronal connectivity and delayed circuit maturation, which may extend or shift these windows of plasticity. If so, interventions that stabilize network activity—such as T-type calcium channel modulation—might help enable more effective language development during these periods. This could potentially explain why some improvements, once initiated, continue even after treatment is stopped.

This also raises the possibility that timing may be critical. If language development depends on sensitive developmental windows, and pathways involving CNTNAP2 alter the timing of circuit maturation, then the age at which a treatment is given could determine its effectiveness. Interventions such as T-type calcium channel modulation may be more beneficial when applied during periods of higher neural plasticity, and less effective once circuits have become more established. This could help explain why any signal of benefit has been difficult to detect in routine clinical use.

 

Conclusion

The study did not have a placebo group. We know from many previous small studies that in most cases everyone improved in autism studies, including those who were assigned the placebo.

Has Niesen identified a simple therapy that will improve speech in autism?

If ethosuximide strongly improves language, why has this not already been noticed?

Neurologists have used ethosuximide for decades for autistic children with absence seizures, but it is not widely recognized as a language-enhancing drug.

I expect there likely is a subgroup of responders, but it will not be a silver bullet for all.

Ethosuximide is cheap, but it can have some unusual side effects.

Zonisamide is more predictable than Ethosuximide, but still can have problematic side effects, more so than drugs like bumetanide or atorvastatin.

It may be the case that responders to Ethosuximide do not need to take it permanently and that has to be factored into the side effect assessment.

Any potential benefit is likely limited to a specific subgroup, such as children with subtle absence seizures, epileptiform activity, or abnormalities in calcium channel signaling. One candidate subgroup involves mutations in the CNTNAP2 gene, which are associated with language impairment, autism, and increased neuronal excitability. Preclinical studies suggest that targeting T-type calcium channels in such models can reduce hyperexcitability and improve behavioral features, raising the possibility that drugs like ethosuximide may be more effective in individuals with similar underlying biology.

CNTNAP2 is also regulated by TCF4, the gene mutated in Pitt-Hopkins syndrome, a condition marked by profound speech deficits. This points to overlapping biological pathways underlying language impairment across different neurodevelopmental disorders and reinforces the idea that identifying responders will be key to determining clinical value.

So, another idea for Pitt Hopkins parents is to consider is Ethosuximide. Maybe the parents’ organisation should contact Charles Niesen to make a small clinical trial, like the forthcoming Clemastine one.

Time for T? Targeting language-associated gene Cntnap2 with a T-type calcium channel blocker corrects hyperexcitability driving sensory abnormalities, repetitive behaviors, and other ASD symptoms, but will it improve language? Will it also benefit Pitt Hopkins syndrome (PTHS) and broader autism?

 

  

 

There are at least 2 Natasas I can think of who will like this post.

Today’s post revisits the subject of calcium channels in autism.  Ion channel dysfunctions are a favourite area of mine because many should be treatable by repurposing safe, existing drugs. I do take note that many readers of this blog have reported success by targeting L-type calcium channels.

Many years ago, at the start of this blog, I recall reading about Timothy syndrome and a researcher at Stanford, Ricardo Dolmetsch, who was exploring treatment using a T-type calcium channel blocker.  It turned out that he had a son with severe autism, which was driving his interest at that time. He won all kinds of awards, but I always wondered why he did not treat his own son.

It is quite strange because Timothy syndrome is caused by a gain of function of an L-type channel. This mutation causes the Cav1.2 channel to fail to inactivate properly after opening. As a result, there is prolonged calcium influx into cells.

Instead of blocking Cav1.2, the researchers blocked the T-channels Cav3.2 and 3.3.

I did my homework on idiopathic autism a dozen years ago and concluded I needed to block Cav1.2. I went ahead and did it – it works like a charm.

It was a real drama back in those days, with self-injury and aggression, so Timothy syndrome and T channels remains stuck in my mind a decade later.

 

Language Genes

Even before parents worry about self-injurious behavior (SIB), they go through the phase of worrying about if their child will ever speak. Some do and some do not.  What really matters is communication, rather than speech.

 

FOXP2 - The language Gene

FOXP2 is a transcription factor involved in the development of neural circuits related to speech and language production, particularly in areas such as the basal ganglia and cerebellum. Mutations in FOXP2 can lead to speech and language deficits.

FOXP2 influences motor control and vocalization processes that are critical for speech, and it is thought to have evolved specifically in humans to support complex language abilities.

 

CNTNAP2 - The language-associated gene

CNTNAP2 (Contactin-associated protein-like 2) is a gene that encodes a cell adhesion protein. It plays a critical role in the development of neural connectivity and the formation of synapses in areas of the brain involved in language, such as the broca’s area and temporal lobes. CNTNAP2 is also involved in the regulation of neuronal excitability and is crucial for the development of white matter tracts that connect language-related brain regions.

Mutations in CNTNAP2 have been implicated in neurodevelopmental disorders such as specific language impairment (SLI), autism, and developmental language disorders.

 

FOXP2 and CNTNAP2 Interaction

FOXP2 and CNTNAP2 work together in the development of the neural circuits that are crucial for language and speech. They are both involved in the formation and maintenance of synaptic connections in key brain regions like the cortex, basal ganglia, and cerebellum, which are critical for motor control, vocalization, and language processing.

There is evidence to suggest that FOXP2 may regulate the expression of CNTNAP2 as part of a broader gene network that governs language development. FOXP2 may influence CNTNAP2 gene expression, which in turn impacts neural connectivity and synaptic function in brain regions responsible for speech and language.

 

CNTNAP2 sounds familiar?

We have come across this gene before.

At least one reader has a child with a mutation in this gene.

We also discovered that the Pitt Hopkins gene TCF4 regulates CNTNAP2 and that

“PTHS (Pitt Hopkins syndrome) is characterised by severe intellectual disability, absent or severely impaired speech, characteristic facial features and epilepsy. Many of these features are shared with patients carrying CNTNAP2 mutations, leading researchers to test patients with PTHS-like features for CNTNAP2 mutations”

Several readers have children with PTHS (Pitt Hopkins syndrome).

It is not inconceivable that what works for CNTNAP2 will also work for at least some PTHS (Pitt Hopkins syndrome).

The question is whether what works for CNTNAP2 will work much more broadly and could it even improve language development?

Here is the recent research from Stanford:

 

Reticular Thalamic Hyperexcitability Drives Autism Spectrum Disorder Behaviors in the Cntnap2 Model of Autism

Autism spectrum disorders (ASDs) are a group of neurodevelopmental disorders characterized by social communication deficits, repetitive behaviors, and comorbidities such as sensory abnormalities, sleep disturbances, and seizures. Dysregulation of thalamocortical circuits has been implicated in these comorbid features, yet their precise roles in ASD pathophysiology remain elusive. This study focuses on the reticular thalamic nucleus (RT), a key regulator of thalamocortical interactions, to elucidate its contribution to ASD-related behavioral deficits using a Cntnap2 knockout (KO) mouse model. Our behavioral and EEG analyses comparing Cntnap2^+/+ and Cntnap2^-/- mice demonstrated that Cntnap2 knockout heightened seizure susceptibility, elevated locomotor activity, and produced hallmark ASD phenotypes, including social deficits, and repetitive behaviors. Electrophysiological recordings from thalamic brain slices revealed increased spontaneous and evoked network oscillations with increased RT excitability due to enhanced T-type calcium currents and burst firing. We observed behavior related heightened RT population activity in vivo with fiber photometry. Notably, suppressing RT activity via Z944, a T-type calcium channel blocker, and via C21 and the inhibitory DREADD hM4Di, improved ASD-related behavioral deficits. These findings identify RT hyperexcitability as a mechanistic driver of ASD behaviors and underscore RT as a potential therapeutic target for modulating thalamocortical circuit dysfunction in ASD.

Teaser RT hyperexcitability drives ASD behaviors in Cntnap2-/- mice, highlighting RT as a therapeutic target for circuit dysfunction.

 

Overall, this study identifies elevated RT burst firing and aberrant thalamic oscillatory dynamics in Cntnap2^−/− mice as a key driver of ASD-related behavioral deficits. If this is a common mechanism of ASD-circuit pathology arising from a variety of genetic causes, then compounds such as Z944, or subtype specific T-type calcium channel antagonists that would target the Cav3.2 and Cav3.3 expressed in RT neurons, might be an effective therapeutic strategy. Furthermore, future research should focus on elucidating RT’s roles in sensory, emotional, and sleep regulation to optimize therapeutic strategies in the context of ASD.

 

Existing T-type calcium channel blockers for humans

Mibefradil is one of the most well-known T-type calcium channel blockers. It was initially developed for hypertension and angina because of its ability to block T-type channels. However, mibefradil was withdrawn from the market in 1998 due to serious drug interactions with other medications, particularly those that inhibit liver enzymes involved in drug metabolism, like statins.

Despite its withdrawal, mibefradil has been studied for other potential uses, including in epilepsy and chronic pain, due to its effects on neuronal excitability.

Zonisamide is an anticonvulsant medication that has some T-type calcium channel blocking properties. It is approved for epilepsy and partial seizures, but it is not typically used specifically for Timothy syndrome or conditions involving T-type channel dysfunction.

Zonisamide is also used to treat seizures in pet dogs and cats.  

Zonisamide: chemistry, mechanism of action, and pharmacokinetics

Zonisamide is a novel antiepileptic drug (AED) that was developed in search of a less toxic, more effective anticonvulsant. The drug has been used in Japan since 1989, and is effective for simple and complex partial seizures, generalized tonic-clonic seizures, myoclonic epilepsies, Lennox–Gastaut syndrome, and infantile spasms. In Japan, zonisamide is currently indicated for monotherapy and adjunctive therapy for partial onset and generalized onset seizures in adults and children. In the United States, zonisamide was approved by the Food and Drug Administration (FDA) in 2000 as an adjunctive treatment for partial seizures.

The drug’s broad spectrum of activity and favorable pharmacokinetic profile offer certain advantages in the epilepsy treatment armamentarium. Chemically distinct from other AEDs, zonisamide has been shown to be effective in patients whose seizures are resistant to other AEDs. Zonisamide’s long plasma elimination half-life has allowed it to be used in a once-daily or twice-daily treatment regimen in Japan.

It is believed that zonisamide’s effect on the propagation of seizure discharges involves blocking the repetitive firing of voltage-sensitive sodium channels, and reducing voltage-sensitive T-type calcium currents without affecting L-type calcium currents. These mechanisms stabilize neuronal membranes and suppress neuronal hypersynchronization, leading to the suppression of partial seizures and generalized tonic–clonic seizures in humans.

Zonisamide possesses mechanisms of action that are similar to those of sodium valproate, e.g., suppression of epileptogenic activity and depression of neuronal responses. These mechanisms are thought to contribute to the suppression of absence and myoclonic seizures.

  

Conclusion

It would seem that zonisamide should be trialed in:

·        CNTNAP2-related neurodevelopmental disorder

·        Pitt Hopkins syndrome (PTHS)

·        Timothy syndrome

·        Idiopathic/polygenic autism

(But, don’t hold your breath!)

Due to the nature of CNTNAP2 disorder and PTHS, I think the greatest impact will be if given from a very young age. However, we do see improvements with many autism interventions regardless of age.

It is certainly conceivable that even mild autism can benefit from damping down reticular thalamic (RT) hyperexcitability.

If shown effective, zonisamide would join the long list of anti-epileptic drugs (AEDs) “repurposable” to treat certain subtypes of autism.