Human colonic mucosa possesses a mixed population of 5-HT receptors.

Abstract The aim of this study was to characterise the 5-HT receptor(s) mediating secretory responses of isolated human colonic mucosa to 5-HT. Sheets of muscle-stripped mucosa from proximal (ascending) and distal (sigmoid) human colon were set up in Ussing chambers for measurement of short-circuit current ( I sc ) Serosal application of 5-HT led to non-neural, concentration-dependent increases in I sc . Desensitisation to 5-HT was observed with ascending and sigmoid colonic mucosa. Using selective 5-HT antagonists we have shown that 5-HT induces secretion in sigmoid colon via a 5-HT 2A receptor. In ascending colon a combination of 5-HT 2A and 5-HT 4 receptors appears to be involved.