ETHANOL SUPPRESSION OF NALOXONE-INDUCED WITHDRAWAL IN MORPHINE-DEPENDENT RATS

The technique of morphine pellet implantation was used to produce physical dependence on morphine in male rats. The number of wet dog shakes occurring within a period of 30 min during naloxone-precipitated (1.0 mg/kg, s.c.) withdrawal in 4-day morphine implanted rats was determined after either acute or chronic treatment with ethanol. An acute dose of ethanol administered prior to withdrawal had no significant effect on the withdrawal response; chronic administration of ethanol during the development of dependence on morphine significantly suppressed the naloxone-precipitated withdrawal response to 44-57% of the control response. Analysis of brain and plasma for morphine concentration 4 days following dependence development showed no significant differences between morphine controls and those animals treated with both morphine and ethanol. Pentobarbital demonstrated no effect on the withdrawal response, whether administered acutely or chronically during the development of dependence.