Real-time detection of serotonin release from enterochromaffin cells of the guinea-pig ileum

Serotonin (5-hydroxytryptamine; 5-HT) containing enterochromaffin (EC) cells may detect chemical or mechanical stimuli in the intestinal lumen and respond with release of 5-HT The aim of this study was to use real-time electrochemical detection methods to detect release of 5-HT from small numbers of EC cells. In guinea-pig ileum, basal release of 5-HT from the unstimulated, unparalyzed intestine was composed of individual release events (8.4 +/- 1.8 events, 0.33 +/- 0.06 Hz) of different amplitudes but with similar kinetics. Local compression of the mucosa with the electrode evoked peak 5-HT release of 12.3 +/- 2.8 mumol L-1 with a sustained release of 3.0 +/- 0.7 mumol L-1. Brief application of acetylcholine (ACh) or carbachol elicited a transient peak (5.7 1.3 mumol L-1 occurring at 35 +/- 18 s, n = 9) followed by cyclic release of 5-HT (9.7 +/- 2.2 events, 0.40 +/- 0.13 Hz, n = 6). This study shows that the release of 5-HT occurs rapidly as individual events from a small number of cells and can reach very high concentrations locally.