Psychotropic drugs: mechanism of action at the neurotransmitter level.

Although the intimate mechanism by which psychotropic agents exert their therapeutic effects is still not completely clear, a large bulk of evidence supports the existence of a close correlation between their clinical antipsychotic acitivity and the ability to affect by different mechanisms brain monoamines and/or other real or putative neurotransmitters. Neuroleptic drugs of the phenothiazine type and related classes possess a blocking effect on dopaminergic transmission in nigro-striatal, mesolimbic and mesocortical areas; experiments supporting both a pre-and post-synaptic site of action have been described, together with the interference at the molecular level with DA-sensitive adenylate cyclase activity. In addition, anticholinergic activity and increase in GABA turnover in the striatum have been given as evidence to explain for some neuroleptics (e.g sulpiride, clozapine) lack of extrapyramidal side-effects. Anxiolytics seem to produce their therapeutic effect through a decrease in catecholaminegic and serotoninergic turnover although new avenues have been opened by some recent reports indicating a facilitation of GABAergic and glycinergic transmission in CNS.