异丙酚对大鼠下丘神经元第一动作电位延时的影响

Effect of propofol on first spike latency of rat inferior colliculus neurons

目的评价异丙酚对大鼠下丘神经元第一动作电位延时（FSL）的影响，以揭示异丙酚麻醉导致听觉消失的神经电生理学机制。方法SPF级SD大鼠43只，雌雄不拘，体重200—250g，将玻璃微记录电极置人下丘，用于记录FSL。腹腔注射异丙酚100mg／kg。分别于给药前和给药后每间隔10min记录特征频率下声音强度从90dBSPL至阈下10dBSPL时FSL。采用一阶指数函数分别拟合给药前后不同时点FSL-声音强度曲线。结果1只大鼠下丘神经元呈现撤声反应，给药后10min时FSL延长0．8ms。其余42只大鼠下丘神经元对声音起始部分起反应，与给药前比较，给药后10min时下丘神经元FSL延长（P〈0．05）。给药后不同时间点FSL声音强度一阶指数函数的R2〉0．95（P〈0．05），给药后FSL-声音强度曲线向上平移。结论异丙酚可延长大鼠下丘神经元FSL而抑制听觉信息传递，但并不改变FSL编码的信息含义。

Objective To evaluate the effect of propofol on first spike latency （FSL） of inferior colliculus neurons and explore the electrophysiological mechanisms underlying the propofolnduced loss of hearing. Methods Forty-three SD rats of both sexes weighing 200-250 g were used in this study. FSL was recorded with glass recording micro-electrode inserted in inferior colliculus. Propofol 100 mg/kg was administered intraperitoneally. FSL was recorded before and every 10 min after propofol administration when sound intensity was between 90 dB SPL and t0 dB SPL before threshold. First-order exponential function was used to fit FSL-sound intensity curve at different time points before and after propofol administration. Results The inferior colliculus neurons showed offset response in one rat. FSL extended to O. 8 ms at 10 min after propofol administration. In the remaining 42 rats, the inferior colliculus neurons responded only to the beginning part of the sound. FSL was prolonged at 10 min after propofol administration. R2 of first-order exponential function 〉 0.95 at different time points after propofol administration （P 〈 0.05）. FSL-sound intensity curve was shifted parallelly upwards after administration. Conclusion Propofol affects auditory information transmission by extending FSL of rat inferior colliculus neurons but does not change the meaning of the information encoded by FSL.