Effects of lead exposure on long-term potentiation induced by 2-deoxy- d-glucose in area CA1 of rat hippocampus in vitro

Abstract

Chronic developmental lead exposure is known to be associated with cognitive dysfunction in children. Previous studies have demonstrated that chronic lead exposure could impair the induction and maintenance of long-term potentiation induced by high-frequency stimulation (HFS-LTP). In area CA1 of rat hippocampus, long-term potentiation could also be induced following temporary replacement of 10 mM 2-deoxy- d-glucose (2-DG) for 10 mM glucose in the normal perfusate (artificial cerebrospinal fluid). The present study was carried out to investigate whether chronic lead exposure affected long-term potentiation induced by 2-DG (2-DG-LTP). Neonatal Wistar rats were exposed to lead from parturition to weaning via milk of dams whose drinking water contained 0.2% lead acetate. Field excitatory postsynaptic potentials (EPSPs) in area CA1 of hippocampus were recorded on postnatal days 25–30. 2-DG application was followed by an increase in EPSP slopes in a time-course-dependent manner in both control and lead-exposed rats, while the amplitude of 2-DG-LTP in the lead-exposed rats (225.9±19.0%, n=12) was significantly greater than that in controls (155.2±9.8%, n=12). In contrast to the effects of lead exposure on 2-DG-LTP, the amplitude of HFS-LTP in the lead-exposed rats (121.5±13.7%, n=12) was significantly less than that in controls (183.9±18.6%, n=12). These results indicate that chronic lead exposure had opposite effects on the two types of LTP induced by HFS and 2-DG. This would suggest that the effects of lead on HFS-LTP and 2-DG-LTP are the result of different sites of lead toxicity.