刺激中缝背核压抑大鼠小脑浦肯野细胞对苔状和爬行纤维传入的反应

STIMULATION OF DORSAL RAPHE NUCLEUS INDUCED DEPRESSIVE EFFECT ON CEREBELLAR PURKINJE CELL RESPONSES TO MOSSY AND CLIMBING FIBER AFFERENT INPUTS IN RAT

本文在麻醉并制动的大鼠上观察了中缝背核(DR)条件刺激对由苔状和爬行纤维传入引起的小脑浦肯野细胞(PC)诱发反应的影响。主要结果有:(1)刺激大脑皮层感觉运动区可以引起苔状和爬行纤维向对侧小脑皮层第Ⅵ和Ⅶ小叶的传入,因而在该小叶上记录到 PC 的诱发简单锋电位(SS)和复杂锋电位(CS)反应,潜伏期分别是8—25和12—30ms。(2)以不影响PC 自发 SS 和 CS 活动的阈下强度刺激 DR,可显著地压抑 PC 对于刺激感觉运动皮层引起的苔状和爬行纤维兴奋所产生的诱发 SS 和 CS 反应,这种压抑作用可持续数百毫秒。(3)DR条件刺激对 PC 的诱发 SS 和 CS 反应的压抑作用可以被静脉注射5-HT 受体阻断剂羟甲丙基甲基麦角酰胺所减弱或阻断。上述结果表明 DR 的5-HT 能纤维传入可以降低苔状和爬行纤维对 PC 的突触作用效力,抑或降低 PC 对突触传入的反应敏感性,提示中缝-小脑5-HT,能纤维传入系统参与了小脑某些重要的神经活动过程。

In anaesthetized and paralyzed rats,the effect of dorsal raphe(DR)condi-tioning stimulation on cerebellar Purkinje cell(PC)responses to mossy fiber andclimbing fiber inputs were examined.The main results are as follows:(1)Sti-mulation of cerebral sensorimotor cortex elicits widespread activation of mossyand climbing fiber inputs to PCs in contralateral Ⅵ and Ⅶ loubles of the cerebel-lum and generates two kinds of evoked responses,i.e.the simple spike(SS)andthe complex spike(CS)responses with respectively a latency 8—25 and 12—30ms.(2)These PC responses could be markedly suppressed by stimulation of DRat intensities which by themselves were subthreshold for directly affecting PC'sspontaneous SS and CS activities.(3)This DR-induced depressive effects onevoked PC's SS and CS excitations could be attenuated or blocked by systemicadministration of 5-HT receptor blocker methysergide.These results demo-strate that serotonergic fiber input from DR can suppress the efficacy of mossy andclimbing fiber synaptic action on PC,or decrease the responsiveness of PC itselfto afferent synaptic action.The findings of this study also suggest that the raphe-cerebellar serotonergic fiber afferent system may be involved in some of the impor-tant neuronal processings in the cerebellum.