Abstract

Serotonin_2c (5-HT2C) receptors are widely expressed in the central nervous system where they play a pivotal role in the regulation of neuronal network excitability. Along with this fundamental physiological function, 5-HT_2c receptors are thought to be implicated in the pathophysiology of several neuropsychiatric disorders and have become a major pharmacological target for the development of improved treatments of these disorders. In the past decade, many studies have focused on the constitutive activity of 5-HT_2c receptors and the therapeutic potential of drugs acting as inverse agonists. Although the constitutive activity of the 5-HT_2c receptor has been clearly described in vitro, the transposition of this concept to living animals is often difficult to ascertain. Nevertheless, cumulating evidence has demonstrated the functional relevance of such property in regulating physiological systems in vivo both at the level of the central and peripheral nervous systems. The present review provides an update of the growing number of studies that show, by means of pharmacological tools, the participation of the constitutive activity of 5-HT_2c receptors in the control of various biochemical and behavioural functions in vivo and emphasizes the functional organization of this constitutive control together with the phasic and tonic (involving the spontaneous release of 5-HT) modalities of the 5-HT_2c receptor in the brain.

Keywords: Basal ganglia, c-Fos expression, constitutive activity, dopamine release, 5-HT_2c receptor, motoneuron excitability, orofacial activity, rabbit head bobs.