关键词: 海马, 突触, 长时程增强, 记忆, 动物, 实验

Abstract: To investigate the effect of midazolam on the synaptic long-term potentiation (LTP) in the CA₁ region of rat hippocampal slices，and elucidate the mechanisms underlying the effect of midazolam on memory. Methods Hippocampal slices (400 μm thick) were obtained from the brains of 126 male Sprague-Dawley rats that were decapitated.The slices were incubated in artificial cerebrospinal fluid (ACSF) at room temperature for at least 120 min before use.Forty-two slices were randomly divided into 6 groups (n=7): control group， midazolam groups with doses of 0.1,0.5,1.0,2.0 and 5.0 μmol•L^-1. All the slices in each group were perfused with ACSF,midazolam 0.1,0.5,1.0,2.0 or 5.0 μmol•L^-1,respectively.Extracellular microelectrode recording technique was performed to record the evoked population spikes (PS) in CA₁ region.Another eighty-four slices were randomly divided into 12 groups (n=7):LTP group,midazolam-LTP groups with doses of 0.1,0.5,1.0,2.0,5.0 μmol•L^-1,picrotoxin group,bicuculline group,CGP35348 group,picrotoxin + midazolam group,bicuculline + midazolam group and CGP35348 + midazolam group.All the slices in each group were perfused with ACSF and the drugs that were applied in according groups.PSs were recorded for at least 30 min before LTP in each group.For LTP induction,high-frequency stimulation (HFS) conditioning pulses (100 Hz/s) were applied to the Schaffer collateral-commissural pathway of hippocampus using bipolar stimulating electrode. The changes in PS amplitude after HFS were analyzed in each group.Results The PS amplitude of the rat hippocampal slices in midazolam 1.0,2.0 and 5.0 μmol•L^-1 groups were significantly decreased compared with control group (P<0.05 or P<0.01).The PS amplitude in LTP group after HFS was significantly increased by 52%±12% compared with pre-HFS(P<0.01).The PS amplitude was not significantly changed after HFS in midazolam-LTP 0.1 μmol•L^-1　group,when compared with LTP group(P>0.05). Compared with LTP group,the PS amplitudes in midazolam-LTP 0.5,1.0,2.0 and 5.0 μmol•L^-1 groups after HFS were decreased significantly (P<0.01).The PS amplitudes after HFS in picrotoxin + midazolam group and bicuculline + midazolam group were dramatically increased compared with pre-HSF and midazolam-LTP 2.0 μmol•L^-1 group (P<0.01),but there was no difference compared with LTP group(P>0.05).The PS amplitude after HFS in CGP35348 + midazolam group had no significant difference compared with pre-HSF and midazolam-LTP 2.0 μmol•L^-1 group(P>0.05),but it was significantly lower than that in LTP group (P<0.01). Conclusion The inhibition of LTP induction in hippocampus of rats may contribute to midazolam-induced deficits in memory,and the underlying mechanism is involved in the activation of γ-aminobutyric acid (GABA)A receptor in hippocampus.

Key words: hippocampus, synapses, long-term potentiation, memory, animals, laboratory