The effects of developmental and/or direct lead exposure on FR behavior in the rat.

In the present study, 21-day old female rats were exposed to daily doeses of 750 mg/kg of lead acetate via restricted water intake regimen for 70-80 days prior to mating. Treatment was then continued throughout gesation and nursing. At weaning, litters from half of the treated and control mothers were placed on treatment for the remainder of the experiment. This manipulation yielded four groups for testing: Group Pb/Pb, developmental and direct, postweaning exposure; Group Pb/C, developmental exposure only; group C/Pb, direct exposure only; and Group C/C, no exposure to lead acetate treatment. Beginning at 42--49 days of age, offspring were shaped to bar press on a Fixed Ratio 20 (FR20) schedule of reinforcement and then received 20 sessions each 20 min in length. Analyses revealed that Group Pb/Pb received significantly fewer reinforcements/min across sessions that the other three groups and also took significantly longer to emit each 20 response block. Contrary to previous reports in the literature, it is suggested that rats may not be impervious to postweaning lead exposure, particularly when there is a history of developmental exposure.