What's The Deal With Receptor Density?

dookie

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So there's been a fair amount of talk about "receptor density" on the forums lately, with @haidut posting some studies showing that anti-serotonin drugs like cyproheptadine decrease the 5-HT (serotonin) receptor density in the brain. What exactly does this mean? It seems Ray Peat is not fond of talking about "receptors"; he doesn't believe in their existence?

If a drug lowers receptor density of serotonin, does it mean that less serotonin will be able to provoke a greater response, or the opposite (more serotonin is needed to induce "high serotonin symptoms").

Do we want a high or low receptor density of dopamine? of serotonin?
 

haidut

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So there's been a fair amount of talk about "receptor density" on the forums lately, with @haidut posting some studies showing that anti-serotonin drugs like cyproheptadine decrease the 5-HT (serotonin) receptor density in the brain. What exactly does this mean? It seems Ray Peat is not fond of talking about "receptors"; he doesn't believe in their existence?

If a drug lowers receptor density of serotonin, does it mean that less serotonin will be able to provoke a greater response, or the opposite (more serotonin is needed to induce "high serotonin symptoms").

Do we want a high or low receptor density of dopamine? of serotonin?

Cypoheptadine actually INCREASES receptor density. Antagonists typically increase and agonists decrease density. With or without receptors it is another way of saying that the cell will adapt and become less or more responsive to the chemical you are administering depending on whether you are administering antagonist or agonist. Google for "receptor desensitization", this too big of a topic to cover in a single post.
 
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dookie

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Cypoheptadine actually INCREASES receptor density. Antagonists typically increase and agonists decrease density. With or without receptors it is another way of saying that the cell will adapt and become less or more responsive to the chemical you are administering depending on whether you are administering antagonist or agonist. Google for "receptor desensitization", this too big of a topic to cover in a single post.

Couldn't you argue then that cyproheptadine makes you more sensitive to serotonin, so that if you a few days after cypro, eat a serotonergic food, it will cause greater symptoms than had you not taken cypro?
 

haidut

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Couldn't you argue then that cyproheptadine makes you more sensitive to serotonin, so that if you a few days after cypro, eat a serotonergic food, it will cause greater symptoms than had you not taken cypro?

Unless you have carcinoid syndrome, serotonin synthesis has a negative feedback mechanism and it depends on receptor "sensitivity". So, high receptor sensitivity would mean less serotonin needs to be produced. It is a similar idea to the insulin sensitivity. So, cyproheptadine by upregulating receptor sensitivity should lead to less serotonin production AFTER you stop serotonin. There may or may not be higher serotonin synthesis while you take cyproheptadine due to the body thinking it has less serotonin than usual. But human studies show that the latter does not happen - i.e. taking cyproheptadine does not increase serotonin production while using the drug.
 

Mr Joe

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@haidut Does it mean that dopamine agonist such as Lisuride or Metergoline would decrease dopamine sensitivity and increase the quantity needed to impact mood ?
 

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