CHRONIC EXPOSURE TO ENVIRONMENTAL LEVELS OF LEAD IMPAIRS INVIVO INDUCTION OF LONG-TERM POTENTIATION IN RAT HIPPOCAMPAL DENTATE

This study examined the effects of chronic developmental lead (Pb) exposure in rats on hippocampal long-term potentiation (LTP). Male offspring were exposed to 0.2% Pb acetate continuously from birth until testing at 85-105 days. Excitatory postsynaptic potential (EPSP) and population spike amplitudes were measured in the dentate hilar region in response to stimulation applied to the lateral perforant path. LTP was induced in control animals with an average maximal EPSP potentiation of 41%, which was significantly greater than the increase in EPSP amplitudes (2%) in exposed animals after tetanizing stimulation. Current-voltage curves in controls demonstrated significant increases in EPSPs and population spikes after application of pulse trains to induce LTP, while exposed rats exhibited no discernible change in responses. These findings suggest that induction or development of LTP in the dentate hilar region in vivo is impaired by chronic developmental exposure to environmentally relevant levels of Pb.