咪唑安定对大鼠海马脑片突触长时程增强效应的影响

目的：观察咪唑安定对大鼠海马脑片突触长时程增强(LTP)效应的影响，并探讨其影响记忆的机制。方法：126只雄性SD大鼠，断头后取出海马组织，制备400 μm海马脑片。取42张脑片，随机分为6组(n=7)：对照组及咪唑安定0.1、0.5、1.0、2.0和5.0 μmol?L^-1组。各组脑片分别灌流人工脑脊液(ACSF)及咪唑安定0.1、0.5、1.0、2.0和5.0 μmol?L^-1。采用细胞外微电极记录技术，记录海马脑片CA₁区细胞外群体峰电位(PS)的变化。另取84张脑片，随机分为12组(n=7)：LTP组，咪唑安定LTP 0.1、0.5、1.0、2.0和5.0 μmol?L^-1组，印防己毒素组，荷包牡丹碱组，CGP35348组，印防己毒素+咪唑安定组，荷包牡丹碱+咪唑安定组，CGP35348+咪唑安定组。各组脑片分别灌流ACSF及其他各组相对应药物。海马脑片记录PS 30 min后，施以100Hz的高频强直刺激(HFS)，诱发LTP，观察各组脑片HFS后PS幅值的变化。结果：与对照组比较，咪唑安定1.0、2.0和5.0 μmol?L^-1组给药后PS幅值明显降低(P<0.05或P<0.01)。LTP组HFS后PS幅值增高，较刺激前增加了52%±12% (P<0.01)。与LTP组比较，咪唑安定LTP 0.1 μmol?L^-1组HFS后其PS幅值无明显改变(P>0.05)，咪唑安定LTP 0.5、1.0、2.0及5.0 μmol?L^-1组HFS后其PS幅值均明显降低(P<0.01)。印防己毒素+咪唑安定组、荷包牡丹碱+咪唑安定组HFS后PS幅值与HFS前和咪唑安定LTP 2.0 μmol?L^-1组比较均明显增加(P<0.01)，与LTP组比较差异无显著性(P>0.05)。CGP35348+咪唑安定组HFS后PS幅值与HFS前和咪唑安定LTP 2.0 μmol?L^-1组比较均无明显改变(P>0.05)，与LTP组比较明显降低(P<0.01)。结论：咪唑安定能够抑制海马LTP的形成而影响记忆功能，其作用机制与活化海马γ-氨基丁酸(GABA)_A受体有关。

Effect of midazolam on synaptic long-term potentiation in hippocampal slices of rats

Objective 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.