Behavioral toxicity of chronic postweaning lead exposure in the rat.

Effects in the rat of chronic postweaning exposure to 50, 300, or 1000 ppm lead acetate in drinking water were assessed on responding maintained by a fixed-interval 30-s food reinforcement schedule. On this schedule, food reinforcement followed the first lever press response occurring at least 30 s after the preceding food delivery. Exposure to 50 and 300 ppm lead acetate increased response rates and intersubject variability, while latency, or time to initiation of responding in the interval, decreased. Exposure to 1000 ppm initially decreased rates and increased latency values. Following termination of exposure to 50 ppm, response rates and latency values gradually returned to control levels. Behavioral effects produced by exposure to 50 and 300 ppm lead were similar in magnitude but varied in time to onset and decline, suggesting time-dependent, rather than concentration-dependent effects of lead.