CADMIUM EXPOSURE ATTENUATES THE INITIATION OF BEHAVIORAL SENSITIZATION TO COCAINE

Employing a paired-watering procedure to control for differential flui d intake confounds, adult male rats were exposed in the home cage to w ater containing 100 ppm cadmium chloride, or a control solution contai ning no added cadmium chloride. On Day 61 of exposure to their respect ive watering regimens, half the animals from each condition received 1 2 repeated daily i.p. injections of 10 mg/kg cocaine-HCl, or saline. L ocomotor activity (total distance traveled) was recorded in Digiscan A ctivity Monitors for a 20-min baseline period prior to each injection, and for a 40-min period post-injection. On Day 13 of testing, all ani mals received saline injections only in the test chambers, in an effor t to evaluate the role of conditioned cues in the expression of cocain e sensitization. On Day 14-16 of testing, all animals received success ive daily challenges of 10, 20, and 40 mg/kg cocaine in the test chamb er. The results indicated that the initiation (development) of behavio ral sensitization to 10 mg/kg cocaine was attenuated in cadmium-expose d rats. Moreover, the supersensitivity to higher doses of cocaine duri ng dose-effect testing that was registered by control animals pretreat ed with cocaine, was not evident in cadmium-exposed pretreatment anima ls. These data suggests that environmental contaminants may alter drug responsiveness, and thereby may influence patterns of drug selection and use.