异丙酚对大鼠海马CA1区突触传递可塑性的影响

Effects of propofol on synaptic transmission between hippocampal CAl neurons and synaptic plasticity

目的研究异丙酚对海马CAl区突触传递和可塑性的影响。方法断头分离Wistar大鼠海马半脑,制备400μm厚度海马脑片。45张脑片分为六组。脂肪乳剂组和异丙酚组的脑片以印防己毒素预孵30min,然后加入450μl脂肪乳剂或异丙酚(相当于500μmol/L),观察对兴奋性突触后电流(EPSC)的影响。脂肪乳剂长时程增强(LTP)组、脂肪乳剂长时程抑制(LTD)组、异丙酚LTP组、异丙酚LTD组的脑片以90μl脂肪乳剂或异丙酚(相当于100 μmol/L)预孵60 min,给予高频刺激(HFS)或低频刺激(LFS),记录LTP或LTD的发生情况。结果 脂肪乳剂对EPSC无影响(P>0.05);500 μmol/L异丙酚使2/3细胞EPSC下降至基础值的67.5％(P<0.05),使1,3细胞EPSC上升至基础值的140.3％(P<0.05)。脂肪乳剂LTP组给予HFS后EPSC值为基础值的151.6％(P<0.05),脂肪乳剂LTD组给予LFS后EPSC值为基础值的57.9％(P<0.05);异丙酚LTP组给予HFS后,LTP可以产生但不能维持,HFS后EPSC值为基础值的98.8％(P>0.05),异丙酚LTD组给予LFS后EPSC值为基础值的40.8％(P<0.05),明显低于脂肪乳剂LTD组(P<0.05)。结论异丙酚对大鼠海马CAl区突触传递具有双重影响,出现抑制和兴奋两种效果;异丙酚损害大鼠海马CAl区锥体神经元LTP的维持而易化LTD。

Objective To investigate the effects of propofol on synaptic transmission between hippocampal CAI neurons and synaptic plasticity using whole-cell patch clamp technique. Methods Fifty male Wistar rats (13-19 days old) weighing 40-60 g were killed by cervical dislocation. The hippocampi were removed and sliced (400 μm thick). The slices were incubated in artificial cerebro-spinal fluid (CSF) aerated with 95% O2 and 5% CO2 for 2 h and then transferred to recording chamber perfused at 2 ml·min-1 with artificial CSF equilibrated with 95% O2-5% CO2. Forty-five hippocampal slices were divided into 6 groups : (1) intralipid (n=6); (2) propofol ( n =15); (3) intralipid-long term potentiation(LTP) (n=6) ; (4) intralipid-long term depression(LTD) (n=6); (5) propofol-LTP (n=6); (6) propofol-LTD (n=6) . In intralipid and propofol groups (group 1 and 2) the hippocampal slices were first incubated with picrotoxin 50 μmol·L-1 (a GABAA receptor non-competitive antagonist) for 30 min and the baseline values of excitatory postsynaptic currents (EPSCs) were recorded for 10 min, then intralipid 450 (μl or propofol 500 (μmol·L-1 was added to the perfusate and EPSCs were recorded for another 40 min. In group 3-6 hippocampal slices were incubated with intralipid 90 (μl or propofol 100 μmol·L-1 for 60 min and the EPSCs were recorded. The collateral / commisural pathway was stimulated with high frequency stimulation (HFS) or low frequency stimulation (LFS) and EPSCs were recorded. The holding potential was set at - 20 mV during HFS and -50 mV during LFS. Results (1) Intralipid did not significantly change EPSCs ( P> 0.05 ) ; propofol 500 /μmol·L-1 had dual effects : in 2/3 cells EPSCs were reduced to 67.5 % of the basiline values ( P <0.05), while in 1 /3 cells observed EPSCs were increased to 140.3 % of the baseline values ( P <0.05) . (2) In intralipid-LTP group (group 3) EPSCs increased to 151.6% of the baseline value after HFS; while in propofol-LTP group (group 5) EPSCs remained unchanged after HPS (98.8% of the baseline value). In intralipid LTD group (group 4) EPSCs were reduced to 57.9% of the baseline value after LFS; while in propofol-LTD group EPSCs were reduced to 4O.8% of the baseline (P<0.05) .Conclusion Propofol has two contrary effects inhibitory and excitatory on synaptic transmission in hippocampal CA1 in rats, and impairs the maintenance of long term potentiation (LTP) and enhances the development of long-term depression (LTD) of pyramidal CA1 neurons.