Involvement of 5-HT receptors in the discrimitative properties of indorrenate in a model of conditioned taste aversion

This study evaluated the possible differential participation of serotonin ( 5-hydroxytryptamine. 5-HT) receptors in the stimulus properties of indorena te (INDO) using a conditioned taste aversion paradigm. Male Wistar rats dep rived of water were trained in 22 sessions to discriminate INDO from saline , on each session a drug-trial or saline-trial was presented following a ra ,,dom sequence. On drug trials, the administration of INDO preceded the pai rings of saccharin-LiCl, while on saline trials saline administration prece ded the saccharin-saline pairings. Different doses of INDO and of the 5-HT antagonists 8-hydroxy-2-(di-n-propylamino)tetralin)8-OH-DPAT (5-HT1A), 5-me thoxy-3-(1,2,3,6-tetrahydropyridin-4-yl-1H-indole) (RU249S9) (5-HT1A/1B), 6 -chloro-2-(1-piperazinyl)pirazine (MK212) (5-HT2C) and 2-methyl-5-HT (2-Me- 5-HT) (5-HT3/4) were administered in generalization tests. Subjects consume d saccharin when it was preceded by the administration of saline but avoide d the consumption of saccharin after the administration of INDO. Full dose- dependent generalization was observed with the INDO, MK212 and RU24969, whi le 8-OH-DPAT produced only a partial generalization and 2-Me-5-HT did not p roduce generalization at all. Results indicate that INDO may acquire discri minate properties using a conditioned taste aversion paradigm. The 5-HT18/2 C receptors modulated the discriminative function of INDO, while the 5-HT1A receptors had a minor participation in the stimulus properties of INDO.