Studies on drug dependence (Report 99): Effect of quinine on methamphetamine-induced stereotyped behavior and acute toxicity in rats

Abstract

It has been reported that quinine(Q) can improve the methamphetamine(MA)-induced anorexia in rats. In the present experiments, the effects of Q on MA-induced stereotyped behavior (SB) and acute toxicity were examined. MA was injected s.c.,and Q was given p.o. For SB observation, fixed doses of MA(5 mg/kg) and Q(50 mg/kg) were used, and rats were divided into 4 groups as follows: l.MA alone; 2.Q, 60 min before MA; 3.MA and Q administered at the same time; 4.MA, 60 min prior to Q. They were observed continuously after MA administration, and the latency of onset, duration and intensity of SB were recorded for 8 hr. For studies on acute toxicity, various doses of MA or each in combination with a fixed dose(50 mg/kg) of Q were tested. Deaths were recorded for 3 days after drug administration. The MA-induced SB was found to be potentiated in all of the treatment combined with Q. The intensity and duration of SB in the group administered MA and Q at the same time was similar to Q pretreatment and more potent than that in the group given MA prior to Q. However, onset of SB did not change in when MA was given alone or in combination with Q. The lethality of MA was significantly increased in the group given MA combined with Q. These results suggest that Q can enhance the MA-induced SB and acute toxicity. It may be explained by the influence on the metabolic rate for MA.