The correlation study between spatial memory and hippocampal long term potentiation in rats

Abstract

Objective To investigate the correlation of hippocampal synaptic plasticity with spatial learning and memory under normal and pathological condition, and provide experimental evidence for the coincidence of hippocampal late-phase long-term potentiation (L-LTP) and behavioral experiments. Methods 38 SD rats were randomly divided into two groups, control and AD model. First, Morris water maze was used to test the ability of spatial learning and memory of rats. The escape latencies for rats to search for an underwater platform in 5 days of navigation tests and the swimming time percentage in target quadrant on the 6th day after withdrawing the platform in probe trails were recorded. Then, in vivo hippocampus L-LTP of field excitatory postsynaptic potential (fEPSP) in CA1 region was recorded after delivering high frequency stimulation (HFS). Results Bilateral intrahippocampal injection of 4 nmol amyloid β peptide (Aβ 25-35) significantly impaired spatial learning and memory of rats in water maze tests, as well as in vivo hippocampal L-LTP. In control group, there was a significant negative correlation between the amplitude of fEPSP and the escape latency (r=-0.8306, P<0.01) and a significant positive correlation between the amplitude of fEPSP and the swimming time percentage in target quadrant (r=0.7709, P<0.01). In AD model group, similar correlations were found, with a correlation coefficient of r=-0.7675 (P<0.01) and r=0.8049 (P<0.01), respectively. When putting all data from the two groups together, the hippocampal L-LTP was more correlated with escape latency (r=-0.9124, P<0.01) and swimming time percentage (r=0.9745, P<0.01). Conclusion There is very close correlation between the hippocampal L-LTP and the spatial learning and memory behavior in rats, suggesting that the hippocampal L-LTP may be involved in the electrophysiological mechanism of spatial learning and memory in rats, and the impairment of L-LTP could partly represent the deficits in cognitive function of animals. Key words: Spatial learning and memory; Morris water maze; Late-phase long term potentiation; Amyloid β protein