Pharmacological properties and functions of central 5-HT3 receptors.

5-HT3 receptors or recognition sites have been located in the brain of many animal species and man, and are considered to mediate an increase in cation conductance. The functional relevance of the central 5-HT3 receptors is being established using selective 5-HT3 receptor antagonist ligands, which have been shown to modify behaviour in animal tests that is predictive of an action to reduce anxiety, schizophrenia and cognitive disorders. A remarkable feature of the effect of 5-HT3 receptor antagonists is their ability and potency to control a disturbed behaviour in the absence of effect on normal behaviour. This reveals an important role for 5-HT in different behaviours: indeed, the breadth of action of the 5-HT3 receptor antagonists may be indicative of the critical importance of 5-HT in the control of catecholaminergic, cholinergic and peptidergic systems throughout the forebrain. Precisely how such effects are achieved remains a significant investigative challenge, with the potential for novel therapeutic developments being a major goal.