The behavioral effects of phencyclidine (PCP) were studied in male and female Sprague-Dawley rats to determine if chronic infusions would result in sexually dimorphic effects. Rats were trained to make operant responses for food during 30-min response periods that occurred 4 times each day. After attaining stable baseline behaviors, 10 mg of PCP/kg/day was infused s.c. for 10 days. Females were more profoundly affected than males. In the females, response rates were suppressed to 30-71% of control rates during the first 7 days of infusion. In contrast, response rate in male rats never fell below 77% of control during the infusion period. By the eighth infusion day both sexes had become tolerant to these behavioral effects. After stopping infusions there was clear evidence that behavioral dependence had developed; however, the abstinence effects in males and females were similar. Saturation studies of [3H]dizocilpine (MK-801; (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine) binding to brain membranes were conducted to determine if there were sex-dependent receptor differences. There were no significant differences in Kd +/- S.D. (7.6 +/- 1.5 and 7.1 +/- 0.9 nM for males and females, respectively) or Bmax +/- S.D. (4.1 +/- 0.2 and 4.0 +/- 0.5 pmol/mg protein for males and females, respectively).