Serotonin (5-HT) release and uptake measured by real-time electrochemical techniques in the rat ileum

摘要

Serotonin (5-HT)release and uptake measured by real-time electrochemical tech-niques in the rat ileum. Am J Physiol Gastrointest Liver Phys-iol 295: G1228-G1236, 2008. First published October 16, 2008; -Serotonin (5-HT) is released from the enterochromaffin cells and plays an important role in regulating intestinal function. Although the release of 5-HT is well documented, the contribution of the serotonin reuptake transporter (SERT) to the levels and actions of 5-HT in the intestine is unclear. This study aimed to demonstrate real-time SERT activity in ileal mucosa and to assess the effects of SERT inhibition using fluoxetine. Electrochemical recordings were made from the mucosa in full-thickness preparations of rat ileum using a carbon fiber electrode to measure 5-HT oxidation current and a force transducer to record circular muscle (CM) tension. Compression of the mucosa stimulated a peak 5-HT release of 12 +-6 muM, which decayed to 7 +- ,4 muM Blockade of SERT with fluoxetine (1 muM) increased the peak compression-evoked release to 19+- 9 muM, and the background levels of 5-HT increased to 11 +-7 muM (P < 0.05, n = 7). When 5-HT was exogenously applied to the mucosa, fluoxetine caused a significant increase in the time to 50% and 80% decay of the oxidation current. Fluoxetine also increased the spontaneous CM motility (P < 0.05; n = 1) but did not increase the CM contraction-evoked 5-HT release (P > 0.05, n = 5). In conclu-sion, this is the first characterization of the real-time uptake of 5-HT into the rat intestine. These data suggest that SERT plays an important role in the modulation of 5-HT concentrations that reach intestinal 5-HT receptors.