GRANISETRON, A 5-HT3 RECEPTOR ANTAGONIST, INHIBITED CISPLATIN-INDUCED5-HYDROXYTRYPTAMINE RELEASE IN THE ISOLATED ILEUM OF FERRETS

We investigated the influence of granisetron, a 5-HT3 receptor antagon ist, on the increase in 5-hydroxytryptamine (5-HT) release induced by cisplatin from the isolated ileum of the ferret, a species known to vo mit in response to cisplatin. 2-Methyl-5-MT, a selective 5-HT, recepto r agonist, increased the release of 5-HT from the ferret ileum in a co ncentration-dependent manner within the range of 10(-7) to 10(-6) M . The 5-HT release induced by 2-methyl-5-HT was significantly inhibited by a concomitant perfusion with granisetron (10(-6) M). Cisplatin also increased the 5-HT release from the ferret ileum within the range of 10(-8) to 10(-6) M, in a concentration-dependent manner. Granisetron ( 10(-6) M) also significantly inhibited the cisplatin-induced 5-HT rele ase. Since the cisplatin-induced 5-HT release was significantly inhibi ted by tetrodotoxin, the possible involvement of an interneuron pathwa y in the cisplatin-induced 5-HT release mechanism was suggested in the ileal tissue. It is likely that granisetron inhibited the cisplatin-i nduced 5-HT release from the gut EC cells by producing blockade of an EC cell 5-HT3 receptor.