右美托咪定对瑞芬太尼诱导的大鼠脊髓背角神经元NMDA受体mEPSCs的影响

Effect of dexmedetomidine on remifentanil-induced miniature excitatory postsynaptic currents ofNMDA receptors in spinal dorsal horn neurons of rats

目的评价右美托咪定对瑞芬太尼诱导的大鼠脊髓背角神经元NMDA受体微小兴奋性突触后膜电流（mEPSCs）的影响。 方法取出生14～18 d雄性SD幼鼠30只，体重50～60 g，制备腰段脊髓切片，取切片180张，采用随机数字表法分为5组（n＝36）：空白对照组（C组）人工脑脊液中孵育90 min；瑞芬太尼组（R组）在终浓度4 nmol/L瑞芬太尼的人工脑脊液中孵育90 min；低剂量右美托咪定组（L组）、中剂量美托咪定组（M组）和高剂量右美托咪定组（H组）在终浓度4 nmol/L瑞芬太尼和右美托咪定终浓度分别为2、4和6 nmol/L的人工脑脊液中孵育90 min。采用全细胞膜片钳法记录大鼠脊髓背角神经元NMDA受体mEPSCs幅值与时间间隔。 结果与C组比较，其余4组mEPSCs幅值增大，时间间隔缩短（P〈0.05）；与R组比较，L组、M组和H组mEPSCs幅值减小，时间间隔延长（P〈0.05）；与L组比较，M组和H组mEPSCs幅值减小，时间间隔延长（P〈0.05）；与M组比较，H组mEPSCs幅值减小，时间间隔延长（P〈0.05）。 结论右美托咪定可能通过突触前和突触后机制减弱瑞芬太尼诱导的大鼠脊髓背角神经元NMDA受体功能增强。

Objective To evaluate the effect of dexmedetomidine on remifentanil-induced miniature ex- citatory postsynaptic currents （mEPSCs） of N-methyl-D-aspartate （NMDA） receptors in spinal dorsal horn neurons of rats. Methods Thirty male Sprague-Dawley rats, aged 14-18 days, weighing 50-60 g, were used in the study. Their lumbar segments of the spinal cord were immediately removed and sliced. The 180 slices were divided into 5 groups （n= 36 each） using a random number table： blank control group （group C） , remifentanil group （group R） , low-dose dexmedetomidine group （group L） , moderate-dose dexme- detomidine group （group M） and high-dose dexmedetomidine group （group H）. Spinal cord slices were in- cubated in artificial cerebrospinal fluid （ACSF） for 90 min in group C. Spinal cord slices were incubated for 90 rain in ACSF with remifentanil at the final concentration of 4 nmol/L in group R. Spinal cord slices were incubated for 90 min in ACSF with remifentani] at the final concentration of 4 nmol/L and dexmedetomidine at the final concentrations of 2, 4 and 6 nmol/L in L, M and H groups, respectively. The whole-cell patch-clamp technique was used to record the amplitude and time interval of mEPSCs of NMDA receptors. Results Compared with group C, the amplitude of mEPSCs was significantly increased, and the time in- terval of mEPSCs was shortened in the other 4 groups （P〈0.05）. Compared with group R, the amplitude of rnEPSCs was significantly decreased, and the time interval of mEPSCs was prolonged in L, M and Hgroups （P〈0. 05）. Compared with group L, the amplitude of mEPSCs was significantly decreased, and the time interval of mEPSCs was prolonged in M and H groups （P〈0.05）. Compared with group M, the ampli- tude of mEPSCs was significantly decreased, and the time interval of mEPSCs was prolonged in group H （P〈0. 05）. Conclusion Dexmedetomidine weakens remifentanil-induced enhancement in the function of NMDA receptors in spinal dorsal horn neurons probably via the presynaptic and postsynaptic mechanisms in rats.