GLUTAMATE ANTAGONISTS PREVENT MORPHINE-WITHDRAWAL IN MICE AND GUINEA-PIGS

The effects of excitatory amino acid antagonists on increased cortical acetylcholine release and behavioural hyperactivity induced by naloxone in morphine tolerant guinea pigs and mice studied. The results show that the N-methyl-D-aspartic acid (NMDA) antagonist MK-801 (0.1-1 mg/kg, i.p.) injected 30 min before naloxone (3 mg/kg, s.c.) dose-dependently prevented the neurochemical and behavioural signs of morphine withdrawal in guinea pigs and mice. The non-selective antagonist glutamic acid diethylester only at 100 mg/kg i.p. reduced the naloxone-induced increase of cortical acetylcholine release without affecting the behavioural changes. These findings indicate that the activation of excitatory amino acid receptors, mainly the NMDA receptors, plays a relevant role in the expression of opiate abstinence.