Posted by linkadge on November 14, 2010, at 17:42:45
In reply to Re: Vilazodone vs Nefazodone - 5-HT receptors, posted by Joe Schmoe on November 14, 2010, at 16:59:13
>He said Vilazodone is a partial agonist and >competes with serotonin (which is a full >agonist) and effectively blocks 5-HT1a >autoreceptors, which are inhibitory if >stimulated, but Vilazodone keeps them from being >stimulated, which allows synaptic serotonin to >rise without any negative feedback mechanism >from 5-HT1a.
I don't know if I agree with that. According to wikipedia, the way an agonist works depends on the amount of neurotransmitter already present:
"Clinically partial agonists can activate receptors to give a desired submaximal response when inadequate amounts of the endogenous ligand are present, or they can reduce the overstimulation of receptors when excess amounts of the endogenous ligand are present."
So I would disagree with the notion that an agonist is always going to behave functionally like an antagonist like this guy is saying.
>Why blockading 5-HT1a would reduce or eliminate >sexual side effects is still unclear to me, >especially if buspar achieves its pro-sexual >effects by stimulating 5-HT1a instead of >blockading it. If stimulation leads to >desensitization eventually then maybe the end >result is the same, higher synaptic serotonin >levels, but why would that be pro-sexual?
I don't think it is as simple as saying that buspar is always going to increase serotonin. Some studies show the opposite. Also buspar is confusing since its metabolites interact with norepinephrine and dopamine systems. A metabolite of buspar is a NE alpha-2 antagonist like the aphrodesiac yohimbine.
>"vilazodone is also a partial agonist at 5-HT1A >and has been shown to increase extracellular 5->HT levels to a higher degree than existing >SSRIs..."
Well I'd have to read the whole article to know what they're getting at here. I personally don't think that serotonin enhancement really has anything to do with the antidepressant effects of SSRI's. Heres a study which shows that chronic citalopram reduces serotonin function in the rat brain. Nobody really knows WTF is going on with these drugs.
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0006797
poster:linkadge
thread:970074
URL: http://www.dr-bob.org/babble/20101107/msgs/970236.html