RESUMO
The presence of nausea and vomiting is problematic for all selective serotonin re-uptake inhibitors (SSRIs), and their usefulness as anti-depressants is limited in this respect. In an attempt to examine the background of SSRI-induced emesis, the present study aims to describe the role of 5-hydroxytryptamine (serotonin:5-HT) from the viewpoint of 5-HT release in the mouse-isolated ileum. In this study, it was demonstrated that 5-HT release from the mouse-isolated ileum was significantly increased by fluvoxamine at a concentration of 10(-6) M. Also, it was demonstrated that granisetron, a 5-HT3 receptor antagonist, inhibited significantly the increase in fluvoxamine (10(-6) M) -induced 5-HT release. The effect of granisetron on fluvoxamine-induced 5-HT release was occurred in a concentration-dependent manner. The present study demonstrated for the first time that the SSRI-induced increase in 5-HT release from the isolated ileum was significantly inhibited by 5-HT3 receptor antagonist. These results suggest that 5-HT3 receptors might be involved in SSRI-induced 5-HT release from the mouse isolated ileal tissue. Fluvoxamine (10(-6) M)-induced 5-HT release was inhibited concentration -dependently by the concomitant perfusion of diltiazem. The results suggest that L-type calcium channel might be also involved in SSRI-induced 5-HT release from the isolated ileum. Furthermore, tetrodotoxin (10(-6) M) completely inhibited the increase in 5-HT release induced by fluvoxamine. This finding suggests that the increase of 5-HT induced by fluvoxamine involves enterochromaffin (EC) cell stimulation via an inter-neuron pathway in the gastrointestinal tract (GI). SSRI initiates an increase in the concentration of 5-HT in the GI tract. 5-HT released from the EC cells of the intestinal mucosa may stimulate the 5-HT3 receptors on vagal afferent nerve fibers. This depolarization of vagal afferents may result in a 5-HT increase in the brainstem and, thus, lead to emesis.