[Effect of methamphetamine on morphine preference].
The effect of methamphetamine on preference for morphine was studied in rats by the drug-admixed food (DAF) method. The preference rates for morphine-admixed food gradually increased by the repetition of choice and forced trials and then became stable at the level of 70%. On the other hand, the preference rates for morphine-admixed food combined with methamphetamine did not so increase compared with the case of morphine alone. From the taste aversion test, it was assumed that combination of morphine and methamphetamine did not enhance taste aversion, although methamphetamine suppressed development of preference for morphine. In the case of combination of morphine and cocaine or caffeine, preference rates for these drugs increased like the case of morphine. This result indicated that the suppression of the preference for morphine which was induced by methamphetamine was not produced by the general effect of CNS stimulants. We found that methamphetamine suppressed the development of the preference for morphine. These findings suggest that the suppression resulted from neither taste aversion nor the general effect of CNS stimulants. Furthermore, acute toxicity and other effects were enhanced by the combination of morphine and methamphetamine, and it might participate with the suppression.
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002755:Choice Behavior / Q000187:drug effects*; D003042:Cocaine / Q000494:pharmacology; D004338:Drug Combinations; D006801:Humans; D008297:Male; D008694:Methamphetamine / Q000494:pharmacology* / Q000633:toxicity; D009020:Morphine / Q000633:toxicity; D009021:Morphine Dependence; D051381:Rats; D011919:Rats, Inbred Strains; D013649:Taste / Q000187:drug effects
D004338:Drug Combinations; D002110:Caffeine; D008694:Methamphetamine; D009020:Morphine; D003042:Cocaine