INTRAACCUMBENS ADMINISTRATION OF NMDA RECEPTOR ANTAGONIST (+ -)-CPP PREVENTS LOCOMOTOR ACTIVATION CONDITIONED BY MORPHINE AND AMPHETAMINE IN RATS/

In the present experiments the influence of NMDA receptor antagonist ( +/-)-CPP on morphine- and amphetamine-conditioned activation of locomo tor activity was studied in rats chronically implanted with bilateral cannulas in the nucleus accumbens septi. Animals were conditioned by p airing subcutaneous injections of morphine (3.0 mg/kg), amphetamine (1 .5 mg/kg), or saline with a distinctive environment. Following the fiv e drug-environment pairings, rats displayed significant increase in lo comotion when exposed to the drug-paired environment. The expression o f this conditioned response was completely prevented by the bilateral intraaccumbens pretreatment with (+/-)-CPP (1.0, but not 0.1 or 0.3 mu g/mu l/side). These findings suggest that the locomotor hyperactivity conditioned by morphine and amphetamine involves the activation of NM DA receptors within the nucleus accumbens. Copyright (C) 1996 Elsevier Science Inc.