Morphine induced saccharin aversion in α-methyltyrosine pretreated rats

Rats pretreated with l--methyltyrosine (AMT) and then given pairings of saccharin drinking and morphine infusion subsequently showed a reduced preference for saccharin over water, when compared with control rats. Control conditions were AMT pretreatment with saccharin-saline pairings, saline pretreatment with saccharin-morphine pairings, and saline pretreatment with saccharin-saline pairings. A second experiment also showed significantly greater saccharin aversion with morphine-infused, AMT-pretreated rats than with saline-infused, AMT-pretreated rats although the morphine dosage was lower than that used in Experiment 1. These results suggest that morphine is aversive to rats that have been treated with AMT.This research was supported in part by U.S. Public Health Service Grant MH 13570-03.