Posted by SLS on July 31, 2009, at 6:12:18
In reply to Re: Wellbutrin for sexual side effects? » SLS, posted by Sigismund on July 30, 2009, at 21:23:16
> >Risperdal blocks 5-HT2c receptors, the result of which is a reduction in erections and probably libido too. Interestingly, the overstimulation of these receptors might reduce libido.
>
> I thought the reason for the mild prosexual effect of agomelatine, cyproheptadine and mirtazepine was their 5ht2c antagonism?
>
> Not right?
I know you are right, but I am confused as to why. Historically, 5-HT receptor agonists have shown both activation and suppression of sexual behavior, so there has been some conflicting reports regarding receptor function. One confounding aspect of research is that most of it depends on the study of rats. I don't know how valid it is to extrapolate these data to humans. Whereas 5-HT2a receptor stimulation produces increased libido in rats, its blockade in humans does not produce the opposite effect.Under normal conditions, acute stimulation of 5-HT2c receptors can increase libido and produce erections. However, it also delays orgasm. I think it depends on where the receptors are located and whether or not chronic stimulation produces a downregulation. The receptors responsible for erection are located in the brainstem and spinal chord. Perhaps those that reside in the cerebrum play a role in libido. 5-HT1a receptors will hasten orgasm, but inhibit erections. 5-HT7 receptors reduce libido. Perhaps this is why Seroquel, a 5-HT7 antagonist, sometimes increases libido.
It really depends on a balance of 5-HT receptors to control libido, arousal, and orgasm. They are all separate functions. How to resolve a sexual side effect will depend upon which of these three functions are affected. Of course, we cannot forget about the many other biological contributions to sexual libido and response.
I had found a nice piece on the Net not too long ago that explained this stuff, but I can't find it again.
- Scott
poster:SLS
thread:909285
URL: http://www.dr-bob.org/babble/20090721/msgs/909409.html