Behavioral sensitivity to amphetamine after repeated exposure to an organophosphorous pesticide in the rat. Effect of coexposure to restraint.

In the work environment, chemical stressors coexists frequently with physical or psychological stressors. The purpose of the present experiment was to find out whether the effects of a repeated exposure to chlorphenvinphos (CVP), an organophosphorus pesticide, could be modified by a concurrent exposure to restraint, a psychological stressor. The experiment was performed on male Wistar rats. CVP was administered ten times (one injection/day) at doses of 0.5 or 1.0 mg/kg i.p. (1/30 and 1/10 of LD50, respectively) within a period of two weeks. A half of the rats from each group were immobilized in restraint chambers for 120 min/day starting 10-15 min after CVP injection. In each rat, the effect of 0.5 mg/kg of amphetamine (AMPH) and 0.75 mg/kg of scopolamine (SCOP) on motor activity in an open-field was tested three weeks or six weeks (in rats exposed to 0.5 mg/kg or 1.0 mg/kg doses of CVP, respectively) after the last exposure day. No clear cut effect on the behavioral responsiveness to AMPH or SCOP were noted in rats subjected to repeated restraint, repeated 0.5 mg/kg doses of CVP, or combination of these two stressors. In rats exposed to CVP at the 1.0 mg/kg doses, the behavioral response to AMPH was augmented and this effect was not apparently altered in rats coexposed to restraint. The above result indicates that the repeated exposure to CVP may lead to functional alterations within the central nervous system and that coexposure to restraint neither facilitates nor prevents these alterations from development.