D-1 and D-2 dopamine and opiate receptors are involved in the restraint stress-induced sensitization to the psychostimulant effects of amphetamine

The time course of the restraint stress-induced sensitization to the stimulant effects of amphetamine (AMPH, 0.5 mg/kg IP) on locomotor activity was investigated for up to 8 days. In a series of separate experiments, the involvement of opioid and dopaminergic mechanisms in the development of acute restraint stress-induced behavioral sensitization were characterized. Both a single restraint session (2 h) and chronic restraint (2 h per day for 7 days) similarly potentiated the effects of AMPH on motor activity. This behavioral sensitization was prevented by the administration of naltrexone (2 mg/kg IP), haloperidol (1 mg/kg IP), sulpiride (60 mg/kg IP) or SCH23390 (0.5 mg/kg IF) 10-20 min prior to restraint. These results indicate that 1) the development of sensitization to amphetamine-induced effects on motor activity does not depend on the length of exposure to stress (acute or chronic), 2) the stimulation of both D-1 and D-2 dopaminergic receptors is necessary for the development of the restraint stress-induced sensitization to AMPH and 3) an opioid system is also implicated in this sensitization process. (C) 1997 Elsevier Science Inc.