Gastrointestinal effects of 5-hydroxytryptamine and related drugs.

This paper deals with the effects of 5-hydroxytryptamine (5-HT; serotonin) and related drugs on the gastrointestinal tract (GIT). The nomenclature and classification of 5-HT receptors, as well as their putative role in the GIT are updated in this review. Besides its effects on the cardiovascular system, which have been extensively described, several lines of evidence suggest a role for 5-HT in regulating gastrointestinal functions. 5-HT is present in the gastrointestinal tissues, and can elicit contraction or relaxation by activation of a wide variety of mechanisms and receptors. At least four main types of receptors (5-HT1, 5-HT2, 5-HT3 and 5-HT4) have been described and all the four types seem to influence the GIT. In this respect, the 5-HT2, and in some cases the 5-HT1 receptors, appear to be present on the gastrointestinal smooth muscle, while 5-HT3 and 5-HT4 are mainly neuronal.