Serotonin Activates Electrolyte Transport via 5-HT2AReceptor in Rat Colonic Crypt Cells

The aim of this study was to demonstrate that 5-HT activates electrolyte transport directly via 5-HT2Areceptor in rat colonic crypt cells. Patch-clamp whole cell recording was performed in isolated crypts to measure the 5-HT-induced changes in electrogenic K+and Cl−currents. Superfusing 5-HT (10 μM) in the bath solution increased both K+and Cl−currents, which were antagonized by the presence of ketanserin (1 μM), a selective 5-HT2Aantagonist, in the bath solution. Mesulergine (1 μM) a 5-HT2Aand 5-HT2Cantagonist, had no inhibitory effect. Strong chelation of the intracellular Ca2+by 5 mM BAPTA inhibited 5-HT-induced currents. 5-HT also failed to activate K+and Cl−currents in the presence of GDPβS (0.5 mM) in the pipette solution. Intracellular administration of GTPγS (0.1 mM) mimicked the stimulatory effect of 5-HT, that was inhibited by 5 mM BAPTA. H-7 (0.05 mM), an inhibitor of protein kinase C, A, and G, did not affect the currents. These data indicate that a G protein-coupled pathway is involved in the activation of electrolyte secretion via 5-HT2Areceptor.