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

[forestglip]

For reference 9 about reserpine, it looks to me like the sentence about it might be wrong. Based on the abstract, there were basically no differences in prolactin release, except that male migraineurs had a less prolonged prolactin release, which is the opposite of what the paper above says:

I don't know what I was thinking, but I'm the one who had it backwards and the description in the paper about this reference was right.

Reserpine - Headache and PRL Release in Migraine (1979, Headache)

Abstract:

Only the control males, however, had returned to basal PRL levels after 24 hours.

Full text:

Serum PRL, after 24 hours, still remains markedly elevated in normal and migrainous females, and in migrainous males. Only normal males have the hormone levels returned to basal conditions at the end of the test; the phenomenon was evident after 12 hours.

The dashed line that comes back down early is healthy males. Everyone else - healthy females, migraine males and migraine females - still had raised prolactin at 24 hours.

So possibly prolonged recovery of prolactin for males with migraine after taking reserpine.

The paper says this about reserpine:

The drug is known to cause depletion of central neurotransmitter stores;6 central deficiency of 5HT and dopamine (DA)

Wikipedia says it blocks the vesicular transporters VMAT1 and VMAT2, thus decreasing the amount of dopamine and other neurotransmitters available for a neuron to signal with.

Reserpine irreversibly blocks the H+-coupled vesicular monoamine transporters, VMAT1 and VMAT2. VMAT1 is mostly expressed in neuroendocrine cells. VMAT2 is mostly expressed in neurons. Thus, it is the blockade of neuronal VMAT2 by reserpine that inhibits uptake and reduces stores of the monoamine neurotransmitters norepinephrine, dopamine, serotonin and histamine in the synaptic vesicles of neurons.

It also says that it can take up to weeks to replenish the VMATs:

As it may take the body days to weeks to replenish the depleted VMATs, reserpine's effects are long-lasting.

So maybe it takes longer for people with migraine to replenish the VMATs. Very speculative at this point, and I'd want to see more evidence, since the effect was only evident in males in this study.

 

[forestglip]

Reserpine: Men with migraines had delayed return of prolactin to baseline compared to healthy men. No difference for women.

Reserpine - Headache and PRL Release in Migraine (1979, Headache)

Abstract:

Full text:


The dashed line that comes back down early is healthy males. Everyone else - healthy females, migraine males and migraine females - still had raised prolactin at 24 hours.

I just noticed the plots for these are exactly the same. So it looks like that book in the first quote might just be compiling results from previous studies. At least for the reserpine finding. Not sure about the sulpiride finding or others.

 

[forestglip]

I figured one of the best places to get insights about the serotonin v. dopamine debate would be in the correspondence explicitly about this topic here: Buspirone Challenge is not a valid Probe of Central 5-HT1A Receptor Function (2004)

So first looking at the paper that prompted the reply:

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Central 5-Ht Receptor Hypersensitivity in Migraine Without Aura (2003, Cephalalgia)
EM Cassidy, E Tomkins, T Dinan, O Hardiman, V O'Keane

(Ted Dinan was an author on the 1992 postviral fatigue prolactin paper. Veronica O'Keane was also an author on that paper as well as the 1995 ME/CFS prolactin paper.)​

The cohort was 12 females with migraine without aura. Depression, IBS, and other significant medical disorders excluded. They were compared to 16 female healthy controls. All testing done during first 5 days of menstrual cycle.

The test was 30 mg oral buspirone.

At baseline, migraine patients had nonsignificantly lower prolactin.

Although migraine subjects had lower baseline (T0) serum PRL than controls (231 ± 12.9 mU/l compared to 285.3 ± 22.7 mU/l), this was not significant (P = 0.07).

The migraine group had a significantly larger prolactin response.

Migraine subjects had a significantly greater mean ΔPRL (1187.2 ± 179.8 mU/l) than controls (298.4 ± 33.8 mU/l) P < 0.001 (Fig. 2). Co-varying for baseline prolactin, state anxiety and depression did not affect these findings, i.e. there was a significant effect of time (F = 21.74; P = 0.002) and a significant group by time interaction (F = 12.89, P = 0.007).

------

The authors took this result as evidence of 5-HT1A involvement in migraine.

These results indicate that there is hypersensitivity of central 5-HT (1A) receptors in migraine without aura.

They do list a lot of reasons that prior evidence suggests serotonin may be involved in migraine, including:

methysergide, a 5-HT antagonist prevented migraine headache

(5-HIAA) is increased in the urine of migraine subjects during attacks

reserpine and fenfluramine and the 5-HT agonist m-chlorophenylpiperazine have been found to induce headache

intravenous 5-HT itself has the potential to relieve migraine headache

agents that treat the acute migraine attack (e.g. the triptan drugs sumatriptan, zolmitriptan) and also those that prevent migraine recurrence, (e.g. amitriptyline, pizotifen, methysergide) interact with 5-HT

during the spontaneous human migraine attack there is an area of persistent activity in the region of the major monoaminergic nuclei (dorsal raphe nucleus (DRN); locus cerulus) of the brainstem

Positron emission tomography has also recently demonstrated increased central 5-HT synthesis capacity in migraine

But I was a bit shocked at this to see that dopamine is not mentioned a single time in this paper (other than in the title of a reference).

They administered a drug which is both a serotonin agonist and a dopamine antagonist, measuring an effect which is potentially controlled by both aspects of this drug, yet only considered the possibility that the observed effect is related to abnormal serotonin receptors. They didn't even say that buspirone is a dopamine antagonist, only calling it a 5-HT1A agonist every time.

Even if the drug was only a serotonin agonist, it still wouldn't be evidence on its own of serotonin receptor hypersensitivity. As they say in the paper, serotonin controls prolactin release via connections to the hypothalamus (they say "in part" but don't state any other avenues, so I assume there is not good evidence of serotonin connections directly to pituitary controlling prolactin).

DRN projections to the hypothalamus are responsible in part for 5-HT-mediated hormonal release, via postsynaptic 5-HT receptors

Which means the hypothalamus still needs to signal to the pituitary to release the prolactin. Maybe through dopamine? A paper they cite says dopamine is the main regulator (Van De Kar 1982):

The regulation of prolactin secretion is primarily under the inhibitory influence of tuberoinfundibular dopaminergic neurons [47].

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Looking at the letter from JA Sattin and JS Login...

They say that there is evidence that dopamine is involved and possibly necessary for prolactin effects of buspirone:

In rat anterior pituitary tissue, buspirone antagonizes the direct inhibitory effect of dopamine on prolactin release, similar to haloperidol (5). In human subjects, pretreatment with the dopamine antagonist metoclopramide abolishes the prolactin response to buspirone (6), arguing against an independent serotonergic component to the buspirone effect.

They cite a review about how dopamine may be involved in migraine:

The evidence that dopaminergic neurotransmission participates in migraine pathophysiology is extensive, and nicely reviewed by Peroutka, who emphasized the role of dopamine receptor hypersensitivity (7).

Concluding, in part, with:

Based on the data presented, one might well substitute the word ‘dopamine’ for ‘5-HT’ in the title of the paper.

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Now looking at the response to that letter from the authors...

They acknowledge that it is possible that dopamine receptors are implicated:

It is certainly possible that the observed differences in hormonal response to buspirone are secondary to changes in sensitivity of other monoamine receptors. Buspirone is known to have antagonist activity at DA-2 receptors and the 5-HT1A antagonist pindolol only partly (but not completely) inhibits the prolactin (PRL) response to buspirone (3, 4). This suggests that the increased PRL response to buspirone in migraine without aura subjects may reflect DA receptor hypersensitivity.

They dispute that there is good evidence of dopamine being involved in migraine (see full comment for the details):

The evidence for dopaminergic mechanisms in migraine deserves to be revisited. While Peroutka (2) cites some evidence from biochemical and neuroendocrine studies in support of DA mechanisms, the evidence is conflicting.

They say that dopamine-specific prolactin challenge findings in migraine are conflicting:

A number of endocrine challenge studies have also examined DA function in migraine. These studies have used drugs active at DA receptors as probes of DA function in attack-free migraineurs and have also reported conflicting findings. Our literature search and paper review of this area have yielded the following: apart from our own study, of the peer-reviewed controlled endocrine studies published in the literature since 1979, only two studies suggest DA hypersensitivity (17, 18), whereas the other four (19–22) suggest either normal or reduced DA sensitivity in migraine subjects between attacks.

The conclusion is that they find the prior evidence for serotonin involvement more convincing:

Our contention is that the evidence for serotonergic mechanisms in migraine is, in contrast to the literature on dopamine, much more persuasive, an observation exemplified in the superior efficacy of 5-HT1B/1D agonist drugs but otherwise beyond the scope of this correspondence.

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I can't comment on the actual evidence of serotonin vs. dopamine involvement in migraine, but even if it was the case that prior evidence strongly pointed to serotonin involvement in migraine, it doesn't make sense to not even mention that one interpretation of the findings in the present study may be dopamine involvement.

 

[bobbler]

Am I reading it right that some of these things tried were 5-ht basically?

If so I’m also thinking that the relationship between serotonin and feeling happy/excited etc is bidirectional too

Which could explain a bind where the better you feel /if you feel too good one day it triggers something else that makes you ill. Even without the ‘because of the exertion to do with excitement’ or ‘probably did more due to feeling so upbeat’ etc.

Other acute triggers: Intense exercise, a sudden drop in blood glucose (hypoglycemia), or sleep deprivation.[1, 2, 3, 4, 5, 6, 7]

I’m hoping these links work in the references. These are suggested by google search but I have pasted as links to the references. I’ll test the pasting leaves a link now and if not I’ll try and paste them individually

EDIT: ok these references aren’t the best and mostly relate to nhs type pages (and the last one an individuals website) - tho one is interesting as it notes eg lists of other medications that can interfere with prolactin, and it’s a long one with some pretty common ones on there like antihistamines and omeprazole type things.

I’m looking up more that are specific to the suggestions of exertion/exercise and will paste at end of this.

The search was to ask about a 30minute prolactin peak (and apparently it’s half life is 20-50mjns) as I wanted to understand what it actually might ‘do’ regarding symptoms if this is some acute peak to whatever it is. Without this ‘temporary’ caveat then all searches tended to get me to papers about maternal or mammary/reproductive related things. But the list was more interesting and extensive on what it affects when it’s short term. And included things like fluid balance and metabolism.

I thought it was interesting it went on to say what can cause such peaks (because a buspirone challenge is interesting for its own reasons including if useful in diagnostics but even more so if this ‘abnormal response’ makes sense as part of anything we experience as a cycle of getting unwell) that the short list included two items under ‘other common causes of the peak’ section - the one on exertion pasted at the start and the other being the (stress of) blood draw itself (which I assume can be somewhat ruled out given other drugs would have had same blood draw.

If any of these references lead us to anything useful where prolactin spike is caused by lots of exertion or sleep deprivation I can’t think through fully what that tells us (particularly without looking up to see more precisely what they mean by those as conditions and in whom) but it seems an interesting factor that wouldn’t have been controlled for in many cfs studies where they might have had people schlep in distances and hang around having hardly slept the night before due to setting an alarm to be there etc.

Currently looking at:

https://journals.physiology.org/doi/full/10.1152/japplphysiol.00004.2002

And

https://pmc.ncbi.nlm.nih.gov/articles/PMC6720127/

And it has some interesting point on page 5 of pdf that the link to prolonged exercise might be linked to body temp:

During prolonged sustained exercise, the prolactin response is proportional to the intensity at which the exercise is performed, and there is a plateau in the level observed. However, extending the duration of the exercise session can result in a graduate increase in the magnitude of the prolactin response [23,24]. This change in prolactin with prolonged exercise seems strongly driven by the elevation in core temperature occurring with the exercise, as cooling an individual mitigates in part the response [25,26]. Remarkably, during the night after a day-time exercise session, there are reports of a two- to three-fold increase in the nocturnal levels of prolactin [27].

And

Circulating prolactin levels increase in the blood during exercise, with the magnitude of the increase approximately proportional to the intensity of the physical activity. Whether there is a specific intensity threshold required to induce a hormonal response is unclear, but most exercise above the anaerobic threshold initiates substantial and rapid prolactin elevations [3]. However, if exercise is intense enough, but of a short-term duration, the peak prolactin response may actually occur after the exercise ends. Interestingly, excessive emotional stress can cause an anticipatory increase in prolactin even before an exercise session begins [3,6].

On the ‘thermal stress’ hypothesis for prolactin the following paper goes further suggesting when fit men were tested then prolactin increased when they were at rest and heated (by external heaters) but not when heated by the same amount when exercising.

Body temperature elevation, exercise and serum prolactin concentrations - PubMed

Ten young healthy normal-weight males were studied in four test situations designed to elucidate the relative role of body temperature increase vs that of exercise per se for pituitary hormone release. Tympanic temperature was recorded continuously during the tests. Elevation of body temperature...

pubmed.ncbi.nlm.nih.gov

I don’t know how great the paper is from methodology but there are some interesting other references below it on the topic of thermal stress vs prolactin.

There is also this one as an experiment on active and passive heating on prolactin. It’s 2003 old and the journal of experimental physiology - I am intrigued the abstract states it used prolactin ‘as a measure of central fatigue’

https://physoc.onlinelibrary.wiley.com/doi/epdf/10.1113/expphysiol.2005.031294

This link is an article by ‘HealthRX medical team’ so more magazine style though there are some articles referenced , it’s making a few points about the issue of measuring prolactin levels in athletes: https://healthrx.com/labs-v2-prolactin/training-impact

And it’s interesting that it notes the effect of a spike in prolactin to intense exercises diminishes with training, but that in over-training syndrome this effect flips

Overtraining Syndrome Flips the Pattern​

Overtraining syndrome reverses this adaptation. When training volume exceeds recovery capacity for weeks to months, hypothalamic dysfunction emerges. The dopaminergic system becomes blunted, and resting prolactin rises. This is one of several hormonal markers used in overtraining assessment alongside low resting LH, low testosterone, elevated cortisol, and suppressed IGF-1.

The 2013 European College of Sport Science / American College of Sports Medicine joint consensus statement on overtraining syndrome listed elevated resting prolactin as a supportive (though not diagnostic on its own) biomarker of hypothalamic fatigue [7].

 

[ScoutB]

But I was a bit shocked at this to see that dopamine is not mentioned a single time in this paper (other than in the title of a reference).

Yes! Thank you haha. This is probably what I was thinking of when I said they seemed to just assume it.

 

[SugarSquared]

it seems an interesting factor that wouldn’t have been controlled for in many cfs studies where they might have had people schlep in distances and hang around having hardly slept the night before due to setting an alarm to be there etc.

This is of course the thing that always makes ME/CFS research so tricky. Exertion and sleep can mess with so much. What I would hope for is that this is not the soul or main reason for the prolactin spike. Something that leads me to believe that that could be true is the fact that similar exaggerated prolactin and response responses are seen in IBS/non-ulcer dyspepsia and migraine. The patients in the studies may not have been as physically active as healthy people, but there are likely not all to the same level of inactivity as us.

 

[Snow Leopard]

I've read and revisited these studies over the years - the last study mentioned the D2 receptor antagonism hypothesis and I'm convinced this is the mechanism for increased prolactin, rather than anything serotonin specific.

I also have highly exaggerated prolactin responses to even mild D2 receptor antagonists.

This also provides some rationale for the benefit of dopamine modulators like low dose abilify...

 

[N_Dina]

I've read and revisited these studies over the years - the last study mentioned the D2 receptor antagonism hypothesis and I'm convinced this is the mechanism for increased prolactin, rather than anything serotonin specific.

I also have highly exaggerated prolactin responses to even mild D2 receptor antagonists.

This also provides some rationale for the benefit of dopamine modulators like low dose abilify...

Do you mind me asking if you have issues with sleep along with ME? If yes, what sleep medications do you take for this bearing in mind this exceptional sensitivity to D2 antagonism?

 

[V.R.T.]

Just had a random thought- would replicating this be the kind of project Audrey Ryback could take on? She has previous in terms of doing a quality replication attempt in terms of her something in the blood paper. So I thought it made sense to ask.

Tagging @chillier

 

[chillier]

I would really like to see this replicated too, we're aware of it and talking about it. I believe if you are administering a drug then you need to have a clinician on board which we dont have easy access to so we are not best poised to do this.

I think the lack of clinicians who are interested in researching mecfs is the bottleneck for this kind of thing. there are other stimulation based studies that I think could be interesting and *relatively* easy like crh stimulation but we need people who are allowed to do it.

 

[SugarSquared]

I also have highly exaggerated prolactin responses to even mild D2 receptor antagonists.

Could you share which D2 receptor antagonists?

 

[Snow Leopard]

Do you mind me asking if you have issues with sleep along with ME? If yes, what sleep medications do you take for this bearing in mind this exceptional sensitivity to D2 antagonism?

I sometimes take antihistamines for sleep and some of them like promethazine are old 'dirty' (not specific) drugs that antagonise d2 receptors.

I've had blood tests that have had rather high prolactin levels, like doctor wants to do a contrast MRI levels, but they seem to be medication induced, like stopping bupropion (which I took briefly) also spiked the levels, only to drop substantially when tested later.

 

[BrokenBeaktheBrave]

I've had blood tests that have had rather high prolactin levels, like doctor wants to do a contrast MRI levels, but they seem to be medication induced, like stopping bupropion (which I took briefly) also spiked the levels, only to drop substantially when tested later.

I've had high prolactin levels too - enough to have contrast MRI and tested for Addison's etc. PRL has been elevated constantly for 10 years now. Seen two endos about it but neither can explain why.

 

[SugarSquared]

I would really like to see this replicated too, we're aware of it and talking about it. I believe if you are administering a drug then you need to have a clinician on board which we dont have easy access to so we are not best poised to do this.

I think the lack of clinicians who are interested in researching mecfs is the bottleneck for this kind of thing. there are other stimulation based studies that I think could be interesting and *relatively* easy like crh stimulation but we need people who are allowed to do it.

@Jonathan Edwards Do you know of any clinicians who could be interested? How do we get them on board?

 

[N_Dina]

I sometimes take antihistamines for sleep and some of them like promethazine are old 'dirty' (not specific) drugs that antagonise d2 receptors.

I've had blood tests that have had rather high prolactin levels, like doctor wants to do a contrast MRI levels, but they seem to be medication induced, like stopping bupropion (which I took briefly) also spiked the levels, only to drop substantially when tested later.

Thank you for your reply.
It’s been exactly the same for me regarding reaction to antidepressants and related meds. I have a tiny prolactinoma (like 2mm) which probably doesn’t cause hyperprolactinemia due to its size and the fact that prolactin decreased substantially after antidepressant cessation.

The endo obviously advised me to get some mental and physical therapy when I asked them about fatigue and extra weight.

PS: sorry if I am spamming about private health issues in this thread.

 

[SugarSquared]

PS: sorry if I am spamming about private health issues in this thread.

I don’t mind it! It’s some interesting things about prolactin that could come in handy or at least give context for what we’re seeing.

 

[jnmaciuch]

I think the lack of clinicians who are interested in researching mecfs is the bottleneck for this kind of thing. there are other stimulation based studies that I think could be interesting and *relatively* easy like crh stimulation but we need people who are allowed to do it.

Yes, can attest this has also been a bottleneck for other research questions I’ve been interested in.

Really the only clinicians willing to do ME/CFS studies are the ones affiliated with dedicated clinics. Anyone else I have talked to simply has no interest or does not remotely feel comfortable given their lack of experience with ME/CFS (even the ones who see a few patients with it through their regular practice). And if you do go through a clinic, you’re kind of locked into whatever their ideas about ME/CFS are.

 

[wallfish]

I think the lack of clinicians who are interested in researching mecfs is the bottleneck for this kind of thing.

Yes, can attest this has also been a bottleneck for other research questions I’ve been interested in.

I know nothing about what is required from a clinician to do these trials, but I wonder: at this point most people in the world probably know someone affected by ME/CFS or long covid. There must be clinicians who would be motivated for personal reasons. Is it realistic to look for such people? Is location important? Or what are the requirements?

 

[Jonathan Edwards]

@Jonathan Edwards Do you know of any clinicians who could be interested? How do we get them on board?

I was scratching around trying to think of someone. The previous work was mostly done by psychiatrists. I think ideally one would want an academic rheumatologist with an interest in fatigue. I have already suggested the idea to my neurologist colleague at Queen Square but did not get a response.

I am not sure about Edinburgh but Ian McInnes in Glasgow is a very intelligent fellow who I came across in the context of rheumatoid. He may be close to retirement now but he might have a younger colleague who might take an interest. The biggest problem I see is that brains and hormones and neurotransmitters are a bit outside the sphere of interest of most rheumatologists.

 

[Jonathan Edwards]

There must be clinicians who would be motivated for personal reasons. Is it realistic to look for such people? Is location important? Or what are the requirements?

It is not that easy. Look at the research in ME/CFS that involves clinicians. Most of it is too poor quality to be interpretable. It is so easy to make mistakes with recruiting subjects and controls, and to mess up protocols so that you get an artefactual result. The first reason for repeating these tests is to be absolutely sure that they were not due to such artefacts.

The clinician needs to have a clear understanding of the biological question, to be committed and to be skilled in research methodology in the way that a chef needs to be when making a créme brulée. This is not boiling an egg.

One person who does come to mind, although not local, is James Baraniuk. James has a very wide understanding across disciplines and has access to patients. He would know of the buspirone test.