Repeated restraint stress reduces the acquisition and relapse of methamphetamine-conditioned place preference but not behavioral sensitization.

The studies for the effects of stress on drug addiction were mostly obtained using sequential exposure to stress and drugs. However, few studies have been conducted on the effects of simultaneous exposure to stress and methamphetamine (METH) on METH-induced reward effects and behavioral sensitization. Thus, we examined the effects of simultaneous exposure to restraint stress and METH on METH-induced addictive behaviors using conditioned place preference (CPP) in mice. During the conditioning period, the mice were exposed to 2 h restraint stress before administration of METH or saline for 4 days. To investigate the effect of restraint stress on drug relapse, the mice were exposed to 2 h of restraint stress for 4 days during the late period of withdrawal. The results showed that the acquisition of METH CPP was impaired by simultaneous exposure to restraint stress and METH administration and the impairment of METH CPP was retained until METH-induced reinstatement. Additionally, based on locomotor activity data measured during METH reinstatement, simultaneous stress exposure during the conditioning phase increased METH-induced locomotor sensitization. We also found that the magnitude of METH-primed relapse was reduced in mice exposed to restraint stress during the late period of withdrawal. Taken together, these findings suggest that simultaneous exposure to restraint stress and METH can reduce the acquisition and relapse of METH-induced addictive behaviors but not behavioral sensitization.