猫扣带回前部内脏与躯体伤害感受神经元膜电学特性的对比研究

A Comparative Study of Membrane Electrical Properties of Visceral and Somatic Nociceptive Neurons of Anterior Cingulate Gyrus in Cats

目的对比研究猫扣带回前部内脏伤害感受神经元与躯体伤害感受神经元膜电学特性,从膜电学方面为阐明内脏痛与躯体痛具有不同感受特性的机制提供实验依据。方法选择成龄猫77只,体质量2.0~3.5 kg,雄雌不限。根据在体微电极记录的扣带回前部神经元对电刺激内脏大神经或隐神经产生的诱发反应的特点及吗啡对该诱发反应的影响,检出具有长潜伏期(≥50 ms)的内脏伤害感受神经元或躯体伤害感受神经元。应用在体微电极向内脏伤害感受神经元或躯体伤害感受神经元内注入波宽50 ms、不同强度(-5 n A^+5 n A)的一系列极化电流,记录神经元膜电学反应,计算膜电学参数。结果在扣带回前部记录了254个内脏伤害感受神经元和172个躯体伤害感受神经元。内脏伤害感受神经元的内脏大神经诱发反应阈值比躯体伤害感受神经元的隐神经诱发反应阈值高;与躯体伤害感受神经元相比,内脏伤害感受神经元的膜电阻、膜电容、时间常数较大。结论扣带回前部内脏伤害感受神经元与躯体伤害感受神经元的膜电学特性存在差异,可能是内脏痛与躯体痛具有不同感受特性的膜电学基础。

Objective To perform a comparative study on membrane electrical properties of visceral and somatic nociceptive neurons of anterior cingulate gyrus（ACG）in cats,so as to provide the experimental basis for elucidating the mechanism of differences in perceptual qualities between visceral pain and somatic pain from the membrane electrical aspects. Methods A total of 77 adult cats,female or male,weighting 2.0 to 3.5 kg were selected for the study. According to the properties of the greater splanchnic nerve（GSN）or saphenous nerve（SN）evoked responses of neurons in ACG and effect of morphine on the evoked responses,visceral nociceptive neurons（VNNs）having the long latency（≥50 ms）GSN evoked responses or somatic nociceptive neurons（SNNs）having the long latency（≥50 ms）SN evoked responses were detected. With a glass microelectrode in vivo,a series of polarizing current of different intensity from-5 n A to ＋5 n A with a 50 ms duration were injected to these neurons in ACG,and the membrane electrical responses of these neurons were recorded. Finally,the membrane electrical parameters of these neurons were calculated. Results Totally 254 VNNs and 172 SNNs were recorded in ACG. GSN evoked response threshold of VNNs were higher than SN evoked response threshold of SNNs. Compared with SNNs,the membrane resistance,the membrane capacity and the time constant of VNNs were larger. Conclusion Our data proved that there are some differences in the membrane electrical properties between VNNs and SNNs in ACG,which might be the membrane electrical basis for differences in perceptual qualities between visceral pain and somatic pain.