PHOSPHOINOSITIDE SYSTEM-LINKED SEROTONIN RECEPTOR SUBTYPES AND THEIR PHARMACOLOGICAL PROPERTIES AND CLINICAL CORRELATES

Serotonergic neurotransmission represents a complex mechanism involvin g pre- and post-synaptic events and distinct 5-HT receptor subtypes, S erotonin (5-HT) receptors have been classified into several categories , and they are termed as 5-HT1, 5-HT2, 5-HT3, 5-HT4, 5-HT5, 5-HT6 and 5-HT7 type receptors. 5-HT1 receptors have been further subdivided int o 5-HT1A, 5-HT1B, 5-HT1D, 5-HT1E and 5-HT1F. 5-HT2 receptors have been divided into 5-HT2A, 5-HT2B and 5-HT2C receptors. All 5-HT2 receptor subtypes are linked to the multifunctional phosphoinositide (PI) signa lling system. 5-HT3 receptors are considered ion-gated receptors and a re also linked to the PI signalling system by an unknown mechanism. Th e 5-HT2A receptor subtype is the most widely studied of the 5-HT recep tors in psychiatric disorders (for example, suicide, depression and sc hizophrenia) as well as in relation to the mechanism of action of anti depressant drugs, The roles of 5-HT2C and 5-HT3 receptors in psychiatr ic disorders are less clear. These 5-HT receptors also play an importa nt role in alcoholism. It has been shown that 5-HT2A, 5-HT2C and 5-HT3 antagonists cause attenuation of alcohol intake in animals and humans , However, the exact mechanisms are unknown, The recent cloning of the cDNAs for 5-HT2A, 5-HT2C and 5-HT3 receptors provides the opportunity to explore the molecular mechanisms responsible for the alterations i n these receptors during illness as well as pharmacotherapy, This revi ew article will focus on the current research into the pharmacological properties, molecular biology, and clinical correlates of 5-HT2A, 5-H T2C and 5-HT3 receptors.