The buspirone challenge test clearly distinguishes ME/CFS patients from healthy controls: why is it not being developed and deployed?

[forestglip]

I think this may be overthinking the problem. Increased nausea presumably indicates increased signallins somewhere around the hypothalamus. I am not sure that we have any evidence for the conscious sensation of nausea causing any further hypothalamic, autonomic or other signals beyond those that caused the nausea. Maybe it does but it might be hard to prove?

The idea is that it'd be something more like IBS-related. Possibly more to do with the digestive system than the nervous or endocrine systems. Maybe differences in absorption, as you say.

I'm not sure if nausea specifically has been shown to increase prolactin, but stress is well-known to increase prolactin, so the suggestion would be that having nausea or other side effects is stressful, and this increases prolactin higher than normal. As Majeed 1996 notes:

The exact mechanisms of buspirone induced prolactin release in humans and animals are unknown but several pieces of evidence suggest that on balance, prolactin release is mediated by 1. 5-HT receptors, 2. dopamine receptors, 3. non-specific stress factors such as induction of nausea. The latter is highly unlikely as none of our subjects reported any feelings of nausea.

And also Sharpe 1996:

It is of interest that the subjective responses to buspirone, particularly nausea, were greater in the patients with CFS, and similar findings were reported by Bakheit et al. (1992) who used a larger dose of buspirone (60 mg orally). This raises the possibility that the increased prolactin release following buspirone in CFS may reflect a non-specific ‘stress’ response to subjective side-effects.

Against this suggestion, is the absence of correlation between peak nausea ratings and prolactin responses.

It is possible that CFS patients may have, in general, a greater likelihood of experiencing adverse effects of medications. For example, a recent double-blind trial of fluoxetine suggested that fluoxetine may be less well tolerated in patients with CFS than those with major depression (Vercoulen et al., 1996).

 

[Jonathan Edwards]

The idea is that it'd be something more like IBS-related. Possibly more to do with the digestive system than the neural or endocrine systems. Maybe differences in absorption, as you say.

My guess is that nausea from a small molecule like buspirone would be mediated centrally in CNS but I may be wrong.

 

[forestglip]

My guess is that nausea from a small molecule like buspirone would be mediated centrally in CNS but I may be wrong.

Yeah, maybe CNS. Either way, the mechanism of the increased nausea response might be as interesting as increased prolactin response. I just want to make sure we're focusing on the right body system. So it's just a request for researchers to consider this factor in their studies.

 

[bobbler]

My primary concern at this point is whether ME/CFS cases have higher prolactin simply because they have more nausea from buspirone. It just seems like an interesting point that this drug seems to fairly consistently cause both abnormally increased nausea and prolactin.

The evidence against that is that one ME/CFS study (Majeed 1996 thesis) found increased prolactin response but no one reported nausea (which actually seems a little surprising, considering the fairly large sample of 30 individuals in each group all taking the maximum prescribed dose of buspirone, 60 mg).

Also, neither of the fenfluramine studies that saw increased prolactin response reported anything notable about side effects.

It'd still be interesting to investigate why buspirone causes increased nausea even if that was the underlying reason, but it's definitely something important to nail down.

Maybe studies could verify that the increased prolactin response is there even when using drugs that don't cause nausea or other symptoms. Or maybe an anti-nausea drug could be given concurrently with buspirone to see if the prolactin effect is still apparent.

I don’t suppose there was any difference such as keeping the patients lying down during the whole thing in Majeed vs the others? My OI symptoms certainly when they became acute when I was less ill due to eg standing in a queue often included that cold/hot sweat+ nausea as I was about to faint. I had it sitting down too but obviously noticed it as cue to find floor when I was eg in a queue standing etc. So it’s no explanation or sorts it out idea just intrigued about protocol,

I’ve had other tests that lasted a long time done by different providers years apart and one had me lying down on a flat medical couch the entire way through in a quiet clinical room with a single person administering the whole thing in a careful rehearsed way seamlessly

so it was a bit of a surprise when the next time I had it then I was just called in for each bit that was done by different individuals and put back in the waiting room having to refind a chair straight after being injected or blood taken in a chair having been called thru. Plus it was a very hot day.

The first I nearly fell asleep during ie it sort of knocked me out but in a gentle way given the scenario, the other involved near collapse across waiting room and emergency grabbing of wheelchair etc. And all the palaver after (wheeled into a room onto bed still only reclined, people offer sugar etc - thinking back now I’m quite infuriated at how dumb people are due to lack of info, and how closed-minded and presumption-laden that response was, when I needed ‘flat’).

Given they were so many years apart it was astounding how almost identical the results were number-wise tho . It’s amazing to imagine/think that the same symptoms ‘load’ (I might report) when lying down feel very different and lead to very different‘happenings’ when/if being made to do hectic stuff (for me) the whole time…

 

[forestglip]

Oh, sorry, missed this post.

But wasn’t there that study of healthy females at the point in their menstrual cycle where estradiol was the highest and they also had nausea?

Actually, for the buspirone menstrual phase study (Dinan 1990), the highest prolactin response was in the luteal phase, so not when estradiol was highest. Why that would be, I'm not sure.

Also, they don't mention nausea, as far as I can tell, and say the drug was well-tolerated, but they did report increased sedation as a response to buspirone at the time point when the prolactin response was highest.

There may be an aspect of ME/CFS making us more prone to nausea (I get more motion-sickness while in PEM), but I’d be suspicious of that being the reason our prolactin increases. And even if our prolactin rises due to nausea, that’d still be interesting to study.

Agreed.

 

[Axel]

"3. non-specific stress factors such as induction of nausea"

Which study shows this? In the case in question, it would in any event be buspirone that is causing the nausea, and in the case of fluoxetine, they did not test for prolactin.

‘subjective side effects’, ‘non-specific stress’ – aren’t these terms from the field of psychosomatics?

The Q&A section in wich he takes part at the end of a comparative study by Brehan, which sought to invalidate his cohort of depressed patients, leads me to believe that Sharpe is already keen to minimise the findings relating to prolactin (sorry if that sounds Machiavellian).

 

[forestglip]

"3. non-specific stress factors such as induction of nausea"

Which study shows this? In the case in question, it would in any event be buspirone that is causing the nausea, and in the case of fluoxetine, they did not test for prolactin.

‘subjective side effects’, ‘non-specific stress’ – aren’t these terms from the field of psychosomatics?

Good points. The Majeed study that said that didn't cite anything about it, as far as I can see. But to get more specific, here are some studies:

From a review (Freeman et al., 2000) (I haven't looked at the studies cited in this section):

It is clear that prolactin secretion is dramatically affected by “stress.” A myriad of stresses have been used to characterize such effects on prolactin secretion. These include, but are not limited to, the following: ether stress (116, 667, 866, 876, 893, 1077, 1105, 1200, 1257, 1296, 1913), restraint stress (416, 590, 598, 883, 923, 944, 1446), thermal stress (1782a), hemorrhage (274, 883), social conflict (817), and even academic stress in humans (1108).

Lennartsson et al., 2011 found that prolactin increased in males and females in response to a "Trier Social Stress Test":

The stress task in TSST consists of a simulated job interview and a mental arithmetic task, both in front of a committee (two men and one woman), a video camera, and a microphone.

We observed significantly elevated prolactin levels – along with significantly increased plasma adrenocorticotropic hormone (ACTH), serum cortisol, heart rate, systolic blood pressure (SBP), and diastolic blood pressure (DBP) – in response to the stressor. The prolactin response pattern did not differ between men and women, but there was some indication that women might have higher magnitude of response.

Though cortisol also rose after the social stress test, and I think is commonly associated with "stress" in general, and no one has ever described an altered cortisol response to a drug in ME/CFS that I know of. But I don't think they tested cortisol in any of the buspirone studies. (need to double check)

Edit: In Richardson 1995, they tested both cortisol and prolactin responses to buspirone. The difference in cortisol response was not significant (p=.084), while the difference in prolactin response was highly significant (p<.001).

I think that's the only buspirone study that also tested cortisol, but one of the d-fenfluramine studies that found an increased prolactin response in ME/CFS, Cleare et al., 1995, also tested cortisol. Even though prolactin response was higher in ME/CFS, cortisol response did not significantly differ between groups.

 

[Kitty]

For what it's worth, I've been many times more prone to nausea since I got ME/CFS than I was before, and it's triggered by many more things.

One of them is the fatigue and stress of travelling to an appointment and sitting in a waiting room, and another is taking any kind of medication (by mouth or injection). I've learned to ignore it, but if somebody gave me a drug and then asked if I had any side effects, I'd probably tick nausea.

 

[SugarSquared]

Actually, for the buspirone menstrual phase study (Dinan 1990), the highest prolactin response was in the luteal phase, so not when estradiol was highest. Why that would be, I'm not sure.

Also, they don't mention nausea, as far as I can tell, and say the drug was well-tolerated, but they did report increased sedation as a response to buspirone at the time point when the prolactin response was highest.

Thanks for the correction. I remembered there was a side effect, but I forgot which one.

 

[MrMagoo]

Nausea is listed as a common side effect in the BNF

https://bnf.nice.org.uk/drugs/buspirone-hydrochloride/

 

[chillier]

@forestglip No doubt you've discussed this already in this thread but it's become such a big thread! Assuming buspirone acts via D2 receptor antagonism, what do you think the reason for this result could be? Low dopamine levels in the hypophyseal portal system, or a change in sensitivity of the lactotrophs themselves to dopamine?

I'm curious whether this could implicate issues with specifically dopaminergic neurons in the brain in a general sense, or issues with the anterior pituitary in a general sense, or otherwise - though I think you report in your review other endocrine probes for the other hormones don't seem to do much.

 

[hotblack]

I don’t want to speak on behalf of @forestglip but does this answer your question @chillier ?

I think there's a decent chance that the increases in prolactin response are downstream of changes in dopamine D2 receptor density on the pituitary cells. And I think one of the most straightforward things to do is check whether the ME/CFS findings relate to this fairly well-characterized mechanism.

 

[chillier]

I don’t want to speak on behalf of @forestglip but does this answer your question @chillier ?

Cheers @hotblack ! I'm being a bit greedy but I'm curious to know the rationale for the reasoning there - and what characterised mechanism?

In exchange I'll offer this bit of premature overinterpretation from one of the GEM loci (which should be taken with a big pinch of salt, the presentation will hopefully be uploaded soon anyway). One of the loci is nearby a gene called VWDE, which despite the name I don’t think has much to do with blood clotting. The protein atlas single cell data suggest it has restricted expression mainly to the pituitary (and a bit to the thyroid and gonads) to many if not all of the different hormone secreting cells of the anterior pituitary.

 

[hotblack]

Cheers @hotblack ! I'm being a bit greedy but I'm curious to know the rationale for the reasoning there - and what characterised mechanism?

There was a bit more in the full post, but probably better if @forestglip answers

In exchange I'll offer this bit of premature overinterpretation from one of the GEM loci (which should be taken with a big pinch of salt, the presentation will hopefully be uploaded soon anyway).

Ohhhh. Juicy! Nothing like a bit of premature over interpretation and speculation I remember mention of pituitary expression in the thread on the PRIME workshop, but the gene looks intriguing.

VWDE on genecards. Calcium Ion binding and enables Signaling receptor binding….

 

[forestglip]

Assuming buspirone acts via D2 receptor antagonism, what do you think the reason for this result could be? Low dopamine levels in the hypophyseal portal system, or a change in sensitivity of the lactotrophs themselves to dopamine?

I'll push back on the suggestion that the dopaminergic action of buspirone is necessary for the findings to be related to dopamine levels or sensitized lactotrophs. I went into that here:

What it seems like to me is that all of these authors were debating the wrong thing. It's like they considered this a one step process: activate receptor > prolactin goes up. And thus if prolactin goes up too much, it must mean the receptor is abnormal. So researchers were spending their time debating about whether buspirone increases prolactin through the dopamine or through the serotonin receptor. Or how it must all be related to abnormal serotonin if d-fenfluramine causes a response, since that drug is specific to serotonin receptors.

But for some reason - and this still seems so odd to me that I fear I'm the one misunderstanding something - barely anyone was considering that prolactin release is not a one step process. I'm not an expert in these processes, but there are very many steps involved, any of which could be not working right:

The drug binds to the serotonin GPCR. This leads to inhibition of adenylyl cyclase. This decreases cAMP release. This decreases activity of protein kinase A. This decreases positive ion flux into the neuron. This leads to a smaller likelihood of generating an action potential. Assuming this is a dopamine neuron, then this means fewer vesicles bind to the membrane and release their payload of dopamine. Fewer dopamine molecules cross the synapse to reach the lactotroph. There is less inhibition of adenylyl cyclase at the lactotroph. So there is more of all the processes that eventually lead to prolactin vesicles being released.

Why does it have to be the serotonin receptors, and not anything else in that list? Why not "oversensitive" adenylyl cyclase? Or vesicles that bind to the membrane too readily? Or upregulation of dopamine receptors? Or abnormal ion channels? Or a generally sensitized lactotroph?

To put it another way: my sense is if you stimulate point A (serotonin receptors) and notice something weird at point Z (abnormal change in plasma prolactin), then the problem could be anywhere between A and Z (for example, B: hypothalamic neuron ion channels, C: dopamine neurotransmitter vesicles, D: dopamine receptors on lactotrophs, E: lactotroph prolactin vesicles ...). So even if buspirone was acting solely through serotonin receptors, the abnormality could be at the intermediate step of dopamine receptors.

Almost every paper seems to just use a simple interpretation of assuming an abnormality specifically in the receptor at point A, but it seems obvious to me that this is an oversimplification. I could be wrong. But no paper I've seen has explained why they are interpreting it that way.

Anyway..

Assuming buspirone acts via D2 receptor antagonism, what do you think the reason for this result could be? Low dopamine levels in the hypophyseal portal system, or a change in sensitivity of the lactotrophs themselves to dopamine?

I'm curious whether this could implicate issues with specifically dopaminergic neurons in the brain in a general sense, or issues with the anterior pituitary in a general sense, or otherwise - though I think you report in your review other endocrine probes for the other hormones don't seem to do much.

I'm somewhat leaning towards the underlying "cause" of ME/CFS not having anything to do with the pituitary, where these results are just downstream findings of something elsewhere. The purpose of the pituitary is to release hormones into the blood. So if there was something abnormal about it that was causing problems in ME/CFS, I would think that we would have detected it in the blood by now. We do detect this abnormality under a very specific condition of giving a drug, but apart from that, the blood seems normal.

So I'll be a little surprised if genetic findings implicate the pituitary specifically. But maybe.

I'm being a bit greedy but I'm curious to know the rationale for the reasoning there - and what characterised mechanism?

Just my own cautious speculation is basically what I wrote in the "Connection to sex hormones?" part of the review. I'm not sure of the exact mechanism, but my best guess at this point is that sex hormones are over-sensitizing the lactotrophs to dopamine or to stimuli in general. Maybe through increasing numbers of lactotrophs. Maybe through changing density of dopamine receptors.

It just seems like when trying to figure out the mechanism of why prolactin abnormally increases in ME/CFS, the first and most obvious place to consider is the one specific pathway known to increase prolactin response: sex hormones interacting with the pituitary/hypothalamus. (It's the only one I know of that seems to be considered a well-known mechanism for altering prolactin response).

I'm not certain about the above, and even less certain when speculating about why sex hormones would be doing that. Brain damage increasing estradiol seems enticing. Maybe there's some subtle damage to neurons in ME/CFS causing symptoms. This leads to an increase in estradiol, which increases prolactin response as an unrelated consequence. Very little confidence about that though.

My main conclusion is that we have very little data to go on, and the priority should be to get more data through various means.

In exchange I'll offer this bit of premature overinterpretation from one of the GEM loci (which should be taken with a big pinch of salt, the presentation will hopefully be uploaded soon anyway). One of the loci is nearby a gene called VWDE, which despite the name I don’t think has much to do with blood clotting. The protein atlas single cell data suggest it has restricted expression mainly to the pituitary (and a bit to the thyroid and gonads) to many if not all of the different hormone secreting cells of the anterior pituitary.

Yeah, that is interesting. Protein Atlas page: https://www.proteinatlas.org/ENSG00000146530-VWDE/tissue

It'll be good to dig into that gene.

 

[hotblack]

So I'll be a little surprised if genetic findings implicate the pituitary specifically. But maybe.

What about if there was something that gave an extra susceptibility to whatever upstream effect there was. Like something which meant it was more likely for there to be an increase in D2 receptor density? Not that it looks like that’s the case for VWDE which seems more structural, maybe it could affect arrangement or behaviour of lactorphs at that level?

 

[chillier]

I'll push back on the suggestion that the dopaminergic action of buspirone is necessary for the findings to be related to dopamine levels or sensitized lactotrophs. I went into that here:

To put it another way: my sense is if you stimulate point A (serotonin receptors) and notice something weird at point Z (abnormal change in plasma prolactin), then the problem could be anywhere between A and Z (for example, B: hypothalamic neuron ion channels, C: dopamine neurotransmitter vesicles, D: dopamine receptors on lactotrophs, E: lactotroph prolactin vesicles ...). So even if buspirone was acting solely through serotonin receptors, the abnormality could be at the intermediate step of dopamine receptors.

Almost every paper seems to just use a simple interpretation of assuming an abnormality specifically in the receptor at point A, but it seems obvious to me that this is an oversimplification. I could be wrong. But no paper I've seen has explained why they are interpreting it that way.

Presumably there's pharmacological studies that have determined the specificity of the drug for the serotonin and dopamine receptors? Maybe not. I believe that very many drugs are designed to target GPCRs because they are so accessible, varied and can modulate specific signaling pathways. If the drug were to target intracellular components of the signaling pathway there's two issues I can think of. The drug needs to get inside of the cell which is likely to be tricky if it is polarised, then it will require some kind of channel to sneak through. Secondly adenylyl cyclase for example is a signaling protein common to many many upstream gpcrs, so I might imagine inhibiting that would cause chaos or be lethal? Though maybe if you target very particular isoforms of it it would be ok. In any case I found someone has resolved the 3D structure of the serotonin receptors for buspirone in the pdb, so it has specificity for that at least. https://www.rcsb.org/structure/9MD1

Anyway..

I'm somewhat leaning towards the underlying "cause" of ME/CFS not having anything to do with the pituitary, where these results are just downstream findings of something elsewhere. The purpose of the pituitary is to release hormones into the blood. So if there was something abnormal about it that was causing problems in ME/CFS, I would think that we would have detected it in the blood by now. We do detect this abnormality under a very specific condition of giving a drug, but apart from that, the blood seems normal.

So I'll be a little surprised if genetic findings implicate the pituitary specifically. But maybe.


Just my own cautious speculation is basically what I wrote in the "Connection to sex hormones?" part of the review. I'm not sure of the exact mechanism, but my best guess at this point is that sex hormones are over-sensitizing the lactotrophs to dopamine or to stimuli in general. Maybe through increasing numbers of lactotrophs. Maybe through changing density of dopamine receptors.

It just seems like when trying to figure out the mechanism of why prolactin abnormally increases in ME/CFS, the first and most obvious place to consider is the one specific pathway known to increase prolactin response: sex hormones interacting with the pituitary/hypothalamus. (It's the only one I know of that seems to be considered a well-known mechanism for altering prolactin response).

I'm not certain about the above, and even less certain when speculating about why sex hormones would be doing that. Brain damage increasing estradiol seems enticing. Maybe there's some subtle damage to neurons in ME/CFS causing symptoms. This leads to an increase in estradiol, which increases prolactin response as an unrelated consequence. Very little confidence about that though.

My main conclusion is that we have very little data to go on, and the priority should be to get more data through various means.

Interesting, agree about pituitary hormone levels being seen normal in MECFS most likely, and that probably applies to the sex hormones too I suppose. That said, in decodeME hypothyroidism is present in 12% of cases. Seems to be a very common comorbidity amd maybe thats a clue.

 

[forestglip]

What about if there was something that gave an extra susceptibility to whatever upstream effect there was. Like something which meant it was more likely for there to be an increase in D2 receptor density?

I'm not positive of what you mean. A gene expressed specifically in the pituitary which increases [edit: decreases] D2 receptor density might lead to increased prolactin response. But how would it give extra susceptibility to an upstream effect?

 

[Jonathan Edwards]

I don't have a grasp of this but a thought that went through my head is this:

Maybe in ME/CFS pathways related to nociception tend to also stimulate prolactin production but this is compensated for by increased dopaminergic suppression. Buspirone then has a greater effect by blocking an overactive dopamine signalling stream. But the problem isn't anything to do with dopaminergic neurons per se. The nociceptor signalling may be something quite different.

 

[chillier]

I'm not positive of what you mean. A gene expressed specifically in the pituitary which increases D2 receptor density might lead to increased prolactin response.

Is that right? I thought buspirone was an antagonist for D2, and therefore reduces dopamine acting on D2, removing the tonic inhibition on prolactin release and increasing prolactin. So increasing D2 receptor density would increase sensitivity to dopamine and reduce prolactin response if anything?