There are four primary dopamine pathways in the brain:
1. Mesolimbic (hyperactive dopamine signaling here is theorized to cause positive psychotic symptoms);
2. Mesocortical (hypoactive dopamine signaling here is theorized to cause negative psychotic symptoms, cognitive impairment, and possibly contribute to depressive symptoms);
3. Nigrostriatal (hypoactive dopamine signaling here contributes to parkinsonism and if the decreased signaling is due to chemical blockade then tardive dyskinesia can develop as the post synaptic neurons up regulate their D2 receptors); and
4. Tuberoinfundibular (decreased dopamine signaling here results in elevation of prolactin levels)
THE POTENTIAL SIDE EFFECTS ARE:
The typical antipsychotics decrease dopamine signaling by D2 antagonism in all four dopamine pathways, thus they improve positive symptoms of psychosis while increasing prolactin levels, contributing to EPS and tardive dyskinesia, and worsening cognition and negative symptoms. The atypical antipsychotics are more selective, as they decrease dopamine signaling in the limbic system while in some degree sparing the other pathways. Even within the atypical class, there appears to be differential effects.
It is theorized that the advantages of atypical antipsychotics stem from their ability to exploit the ...