离体脊髓运动神经元谷氨酸反应的细胞电生理特征

目的观察离体脊髓运动神经元(MN)谷氨酸(Glu)反应的细胞电生理特征。方法应用新生大鼠(7~19d)脊髓切片MN细胞内记录和细胞旁压力喷射Glu(100 mmol/L,200 kPa,4~300 ms)技术,测量Glu反应的细胞电生理参数,并观察相关药物的影响。结果在23个MN的Glu反应幅度为(14.7±8.8)mV,时程为(24.1±17.3)s,呈现明显的浓度依赖性,反应期间膜电阻减小了(13.1±6.3)%(P<0.001),Glu反应在超极化时增大。用河豚毒素(TTX,0.3μmol/L)预处理后,Glu反应降低为对照的(39.2±28.3)%(P<0.05,n=5)。用TTX和印防己毒素(50μmol/L)预处理后,Glu反应幅度增大为对照的(175.7±67.1)%(P<0.05,n=5);而用TTX、毕扣扣灵(50μmol/L)和士的宁(1μmol/L)预处理后,Glu反应的变化没有显著性意义(P>0.05,n=3)。结论外源性Glu对脊髓MN具有直接兴奋作用,并受到抑制性氨基酸受体的调制。

Cell electrophysiological properties of glutamate-induced responses in spinal cord motoneurons in vitro

Objective To observe the cell electrophysiological properties of glutamate-induced responses in spinal cord motoneurons(MN) in vitro.Methods The intracellular recordings were obtained from MN in neonate rat(7～19 days old) spinal cord slices and the pressure ejection of exogenous glutamate(100 mmol/L,200 kPa,4～300 ms) was made onto the recorded cells.Antagonists of inhibitory amino acid receptors were used by superfusion.Results In 23 antidromically identified MNs,pressure ejection of exogenous glutamate induced depolarization responses with the amplitude of(14.7±8.8) mV and the duration of(24.1 ±17.3) s,which were accompanied by the decrease of membrane resistance(P<0.001).Moreover,the glutamate-induced depolarization was ejection pulse duration(i.e.concentration)-dependent and was increased by membrane hyperpolarization.During pretreatment of tetrodotoxin(TTX,0.3 μmol/L,n=5),the glutamate responses were partially depressed(P<0.05) and the firing spikes were nullified.In the presence of TTX and picrotoxin(50 μmol/L),the glutamate responses were dramatically increased(n=5,P<0.01),while in both of TTX,bicuculline(20～50 μmol/L) and strychnine(1 μmol/L),the glutamate responses did not change significantly(P>(0.05)).(Conclusion) The direct activation of exogenous glutamate on MN may be modulated by the inhibitory amino acid receptors by the postsynaptic mechanism.