Posted by Cam W. on April 16, 2000, at 22:52:07
In reply to Cam - serotonin and dopamine opposition, posted by boB on April 16, 2000, at 21:14:38
boB - I do believe that dopamine and serotonin antagonize each others actions. I can see in my mind's eye the notes that I took at a schizophrenia conference a few years ago. The notes are in my files at work. I will pull them out for a clearer definition than in the example I am going to give you below.An example of this in action is with the atypical antipsychotics (eg Clozaril, Zyprexa, Risperdal, etc.). All of these have a greater affinity for blocking serotonin-2A (5HT-2A) receptors than dopamine-D2 (D2) receptors, but still have action at the dopamine receptors. The mechanism of action of the traditional neuroleptics (eg Haldol, Largacil, Mellaril, etc.) is thought to be dopamine-D2 blockade.
5HT-2A receptors are concentrated in the reticular activating system (raphe nuclei) and in limbic regions. D2 receptors are concentrated in the limbic system and in the prefrontal cortex. So by blocking D2 receptors in the prefrontal cortex you are relieving the postive symptoms of schizophrenia. But (here is where the opposition occurs) by blocking 5HT-2A receptors in the limbic system and sparing dopamine transmission (due to receptor affinity differences) you do not get the movement disorders from the atypical antipsychotics, as you would with the traditional antipsychotics. The 5-HT-2A blockade in the limbic system increase the flow of dopamine, but in the prefrontal cortex (where there is a lack of 5HT-2A receptors) the D2 blockade acts upon the positive symptoms of schizophrenia.
If I remember (and can find my notes) I will post a more insightful answer tomarrow. I will also give you the reference so you can look up the article from where I got this as well. - Cam W.
poster:Cam W.
thread:29285
URL: http://www.dr-bob.org/babble/20000411/msgs/30279.html