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

Abstract 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 μ mol L −1 with a sustained release of 3.0 ± 0.7 μ mol L −1 . Brief application of acetylcholine (ACh) or carbachol elicited a transient peak (5.7 ± 1.3 μ mol 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.