Low-level lead exposure affects latent learning in the rat.

Neonatal rats were administered intragastrically either lead acetate (50 mg Pb/kg-BW) or an equal molar solution of sodium acetate at days 6, 9, 12, 15, and 18 postpartum. At 33 days of age, each animal began a training sequence to develop maze running skills. Animals within each treatment group, i.e., lead exposed (Pb), control vehicle (CV), and control nonhandled (CNH) were assigned randomly to either latent learning or open-field testing groups. The former individually explored a symmetrical maze while satiated; the latter were exposed to an apparatus devoid of barriers. All animals were then food deprived and appetitively tested in the latent learning maze. The Pb, CV, and CNH animals naive to the maze did not differ in maze performance. The CV and CNH animals that previously experienced the maze committed fewer errors than non-experienced counterparts. Pb treated animals showed no evidence of a positive transfer effect of their earlier experience.