咪达唑仑对新生大鼠离体脊髓运动神经元的作用

Effects of midazolam on motoneurons in neonatal rat spinal cord in vitro

目的:观察咪达唑仑对新生大鼠离体脊髓运动神经元(MN)的作用。方法:采用常规细胞内记录技术,观察不同浓度的咪达唑仑对新生大鼠(8～14 d)离体脊髓MN的作用。结果:在5个记录稳定的MN,累积灌流0.1～1.0mmol/L咪达唑仑各15 min,不仅产生可逆的、浓度依赖性去极化反应(P<0.05或P<0.01),并伴有膜电阻的增大(P<0.05),而且抑制动作电位的幅度和发放频率(P<0.05),且1.0 mmol/L的咪达唑仑在其中2个MN完全取消动作电位的产生。在4个记录到背根刺激诱发出兴奋性突触后电位(DR-EPSP)的MN,0.1～1.0 mmol/L咪达唑仑累积灌流各15 min,亦呈现浓度依赖性抑制作用,其中0.1 mmol/L的咪达唑仑对DR-EPSP抑制性作用具有统计学意义(n=3,P<0.05)。而在记录到DR-EPSP合并有抑制性突触后电位(DR-IPSP)的3个MN,低浓度咪达唑仑抑制DR-EPSP而增大DR-IPSP,但高浓度亦完全取消DR-IPSP。结论:咪达唑仑对脊髓运动神经元兴奋性及其外周传入性突触传递具有浓度依赖性抑制作用。

Objective：To observe the effects of midazolam on motoneurons（MNs） in neonatal rat spinal cord slices.Methods：The conventional intracellular recording techniques were used to observe the effects of midazolam at distinct concentration on MNs of spinal cord slices isolated from neonatal rats（8~14 d old）.Results：In the 5 MNs steadily recorded,not only a depolarization response of（18.2±10.8） mV with increase of membrane resistance was induced by perfusion of midazolam at 0.1~1.0 mmol/L for 15 min of each concentration（P0.05 or P0.01）,but also the amplitude of action potential was decreased（P0.05）,and even action potentials were nullified in 2 MNs.In 4 MNs with dorsal rootlet stimulation-evoked excitatory postsynaptic potentials（DR-EPSPs）,bath of midazolam（0.1~1.0 mmol/L） reversibly depressed DR-EPSPs in a concentration-dependent manner.Moreover,in 3 MNs with DR-EPSP followed by inhibitory postsynaptic potentials（DR-IPSPs）,DR-EPSPs were inhibited and DR-IPSPs were enhanced by midazolam at low concentration,whereas both of them were nullified at high concentration.Conclusion：These results suggest that midazolam may reversibly and concentration-dependently inhibit the MN excitability and its synaptic transmission from sensory inputs.