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Thursday, 19 February 2015

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









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



Key points


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

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


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

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

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

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

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

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

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

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




Today’s post has a very odd tittle.

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

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

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

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

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



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



   


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

Function

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



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

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

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

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

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


Abstract

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


Allopregnanolone and mood disorders.

Abstract

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

CONCLUSION:

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

Neurosteroids, GABAA receptors, and escalated aggressive behavior.

Abstract

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


The Do No Harm Principle (Primum non nocere)

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

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

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

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

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

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

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


Experiments in Humans

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

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

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

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

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










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

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

  



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

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





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

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

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


  

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

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


http://www.ncbi.nlm.nih.gov/pubmed/15895085

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



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

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

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

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


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

There is also a pregnenolone cream.

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


  

Effects of modulating multiple binding sites of GABAA

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



or

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

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



Ganaxolone – an altogether better Neurosteroid ?






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

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

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

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


Conclusion

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

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

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

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


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

Mechanism

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

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

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







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

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







4 comments:

  1. Hi Peter,

    I've been trying to locate results on Astra Zeneca's AZ7325 phase 2 trial. The estimated completion date was late last year. Have you managed to find any preliminary findings via your channels?

    On face value, this drug appears promising as a positive allosteric modulator of GABAa subunits alpha2/3 mimicking the effects Clonazepam without the tolerance inducing effects. It appears congruent with your posts on enhancing GABAergic neurotransmission.

    Is this a new drug or an oldie stumbled upon for a new target? Do you see this as an exciting development or just more of much the same?

    For the sake of accuracy and learning please feel free to correct any of my assertions that are incorrect/inaccurate.

    Thanks Peter.

    Regards,
    D&G

    ReplyDelete
    Replies
    1. https://clinicaltrials.gov/ct2/show/NCT01966679?term=AZ7325&rank=1

      The trial is currently recruiting.

      This is a drug that was not found to be effective when first developed, but was well tolerated. Now they are looking for other possible uses.

      I doubt it will be very exciting.

      Delete
  2. Peter,

    Although this research isn't Autism specific, it is related to learning / memory. You may have come across it also.

    http://www.cmu.edu/news/stories/archives/2015/february/synaptic-cloaking-device.html

    I find it interesting because it is counter to what I've traditionally read about Autism and the E/I ratio. I've always believed that the balance has been skewed in favour of excitatory neurotransmission and as such functional improvement could be achieved through mechanisms that seek to shift the balance. Interventions such as low dose Clonazepam acting on GABAa receptors and Bumetanide lowering intracellular chloride.

    The researchers in the linked article identified that when a class of inhibitory neurons called somatostatin cells were turned on they activated the GABAb receptors on hundreds of excitatory neurons in the immediate area which suppressed the excitatory neurons and prevented them from creating and strengthening synapses.

    The researches posit that these somatostatin cells could be a target for improving memory and learning.

    Regards,
    D&G

    ReplyDelete
    Replies
    1. Very interesting.

      Somatostatin is also known as growth hormone-inhibiting hormone (GHIH).

      Various growth factors and hormones are disturbed in autism. One autism treatment (NNZ-2566) from Australia aims to treat this.

      Delete

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