Inhibition Effect of Chronic Lead Exposure on LTP in Rat Hippocampal Dentate Gyrus and Its Mechanism Exploration

After the weanling male Wistar rats were fed 0.2% acetate lead water for 90～108 days,blood lead and brain blood lead,the induction rate of LTP,the concentration of Ca²⁺ and the activities of protein kinase C(PKC) in the neurons of rathippocampal dentate gyrus(DG) were measured in order to probe into the mechanisms of lead induced impairment on learning and memory functions.The results showed that blood lead(4.76±1.08μmol/L) and brain blood lead(0.59±0.06μg/g tissue)in rats of the tested group were obviously higher than that in the control(0.17±0.08μmol/L and 0.06±0.02μg/g tissue,respectively)(P<0.01);the induction rate of LTP and the changes of PS amplitude in the tested group were only 18.2%(2/11) and 120.15±7.15% respectively,and statistically lower than 83.3%(10/12)and 142.70±15.10% in the control(P<0.01 and P<0.05,respectively).Besides that,7 rats in the tested group occured LTD(63.6%).The Ca²⁺ concentration and the PKC activities in cytosol and membrane of hippocampal neurons from lead exposed rats(265.48±53.61mmol/L、1.52±0.40 and 1.87±0.35nmol/min/mg protein,respectively)all significantly increased when comparing with the control(108.81±26.85mmol/L、0.94±0.33 and 1.31±0.29nmol/min/mg protein,respectively)(P<0.01).These results demonstrated that chronic lead exposure can cause adverse effects to the formation of LTP,and suggested that the aberrant increases of Ca²⁺ concentration and the PKC activities in hippocampal neurons may play an importent role in LTP process disturbance associated with lead.