Effects of carbachol on lead-induced impairment of the long-term potentiation/depotentiation in rat dentate gyrus in vivo

The present study aims at evaluating the impairment of LTP and depotentiation (DP) of LTP induced by acute lead exposure, and the effects of peripheral carbachol (CCh) application on LTP/DP of acute and chronic lead-exposed rats in dentate gyrus in vivo. Rats (80–100 days) were acutely exposed to lead by intraperitoneal injection of 0.2% lead acetate (PbAc) solution (1.5 mg/100 g) and/or CCh (1 μg/100 g). Rats were chronically exposed to lead from parturition through adulthood (80–100 days) by the drinking of 0.2% PbAc solution and/or CCh (1 μg/100 g) chronic intraperitoneal injection one week. The input–output (I/O) function, paired-pulse reaction (PPR), excitatory postsynaptic potential (EPSP) and population spike (PS) amplitude were measured in response to stimulation applied to the lateral perforant path. Results showed that: first, acute lead exposure significantly depressed the amplitudes of LTP/DP of both EPSP slope and PS amplitude. Second, CCh significantly increased the amplitudes of both EPSP LTP/DP and PS LTP of acute Pb-exposed rats. After CCh treatment, the magnitudes of EPSP LTP/DP and PS LTP of acute Pb-exposed rats showed no significant difference with controls. Third, Chronic CCh application also reversed chronic Pb-induced impairment of PS LTP and EPSP DP of LTP. As CCh does not cross blood-brain barrier in healthy animals, the data suggest that CCh may traverse BBB in Pb-exposed animals and cure Pb-induced dysfunction of learning and memory.