The effect of inhalation anesthetic on wind up phenomenon of spinal dorsal horn neurons

本文研究了氟烷对猫脊髓宽动态范围（WDR）神经元感受野扩大的影响。将炎性物质角叉菜胶（CG）注射到WDR神经元的外周感受野中心（通常为后爪），诱导扩张。用乌拉坦和氯醛糖麻醉猫，进行腰椎椎板切除术。将填充有3M KCl的玻璃微电极插入脊髓中。用示波器观察和听声法观察大鼠脊髓背角神经元对后爪外周触觉刺激的反应。然后通过机械性、无害性和伤害性刺激或热刺激来确定神经元的性质。对所有刺激方式都有反应的神经元，其对机械刺激的反应与施加的刺激强度成比例地逐渐增加，被认为是WDR神经元。感受野的确定是通过刷毛施加无害的机械刺激来实现的。对照组在注射CG（20mg）后2h感受野开始扩大，4h达最大，并持续到注射后6h。氟烷组从注射CG前20 min开始吸入0.5%氟烷，直至注射CG后2 h。吸入氟烷时，感受野略小于基线。氟烷停药后2h（CG注射后4h），感受野开始扩大，氟烷停药后4h（CG注射后6h），感受野最大。最终扩张水平与对照组相似。上述结果表明，氟烷对注射CG引起的WDR神经元感受野扩大有抑制作用，但吸入时这种作用有限。

We have investigated the effect of halothane on the expansion of the receptive field of the wide dynamic range (WDR) neuron in the spinal cord of cats. The expansion was induced by the injection of an inflammatory agent, carrageenan (CG), into the center of peripheral receptive field of WDR neuron, usually hindpaw. Cats were anesthetized by urethane and chloralose, underwent lumbar laminectomy. A glass microelectrode filled with 3M KCl was inserted into the spinal cord. The activity of spinal dorsal horn neurons were identified by observing oscilloscope and hearing the sound responded to peripheral tactile stimulation of a hindpaw. Then we decided the character of the neuron by giving mechanical innocuous and nociceptive stimulation or heat stimulation. Neurons which responded to all stimulus modality and the response of which to mechanical stimulation increased gradually in proportion to the strength of applied stimuli were regarded as WDR neurons. The receptive field was decided by giving innocuous mechanical stimulation using brush. In the control group, the receptive field began to expand 2 hours after the injection of CG (20mg), reached maximum at 4 hours and remained maximum level until 6 hours after injection. In halothane group, 0.5% halothane was inhaled from 20 min before CG injection until 2 hours after CG injection. The receptive field was slightly smaller than baseline during halothane inhalation. The receptive field began to expand 2 hours after halothane discontinuation (4 hours after CG injection) and reached maximum at 4 hours after the end of halothane inhalation (6 hours after CG injection). The level of expansion was similar to that of control group finally. These results suggest that halothane inhibits the expansion of receptive field of WDR neuron induced by the injection of CG,but this effect is limited during its inhalation.