Conditioned suppression in the adult rat following chronic exposure to lead

Conditioned suppression was examined for control (N = 8) and lead-treated (N = 8) adult rats. Treated animals were exposed daily to 10 mg/kg lead administered via the diet as lead acetate. 40 days of operant lever press training on a multiple schedule using food as reward was given. Lever press training continued for an additional 5 days but during this period subjects experienced superimposed 3 min tone presentations followed by electric shock (1.3 mA, 1.5 s duration) to a grid floor. Tone presentations were observed to be significantly more disruptive of operant steady state responding for treated subjects as compared to controls. This finding supports earlier claims that lead exposure enhances emotionality.