隐神经C类纤维传入诱发小脑皮层电反应

当弱刺激只引起隐神经A类纤维传入时,小脑皮层出现A-CEP,由潜伏期为11.8±3.5ms的早成分和312.1±17.5ms的晚成分组成;当强刺激同时引起A类和C类纤维传入时,出现AC-CEP类似A-CEP;用极化电流选择性阻断A类纤维传导后,只让C类纤维传入时,出现潜伏期为134.2±18.4ms的C-CEP。在Ⅵ小叶蚓部原裂附近C-CEP以正波为主,幅值最大,并在深层位相倒转。C-CEP的潜伏期较长,频率响应较低,幅值较小,随C类纤维传入量而变化,且对镇痛剂较敏感。结果表明C-CEP是由单纯C类纤维传入引起的,在小脑皮层内产生,是小脑皮层对慢痛信息传入的反应。提示C类纤维传入可以到达小脑皮层,引起诱发电位。当A和C类纤维同时传入时,C-CEP不出现,可能是被A类纤维传入所抑制。

ELECTRIC RESPONSES EVOKED BY C-FIBER INPUT FROM SAPHENOUS NERVE IN CAT CEREBELLAR CORTEX

When the A-fibers of the saphenous nerve were stimulated at a lower intensity which elicited the A-fiber input only, an evoked potential (A-CEP) which consisted of an early component with latency of 11.8 +/- 3.5ms and a late component with latency of 312.1 +/- 17.5ms could be recorded on the surface of the cerebellar cortex in cat. When A- and C-fibers were activated by stimulation at the strength of C-fiber suprathreshold, the latency and configuration of the evoked potential had no significant difference from one of the A-CEP. After A-fibers were blocked by the polarizing current, stimulation at the strength of C-fiber suprathreshold could evoke a characteristic C-CEP with latency of 134.2 +/- 18.4ms. In general, C-CEP whose maximal amplitude was recorded on the vermain lobule VI was a positive-negative potential and its phases were reversed in the deep layer of the cerebellar cortex. C-CEP had a smaller amplitude, a longer latency and a lower following frequency than A-CEP had. In comparison with A-CEP, C-CEP had a high susceptibility to the morphine. The results showed that C-CEP which was evoked by the selective C-fiber input and generated in the cerebellar cortex seemed to be a response to the information of the slow pain input. It was suggested that C-fiber input could reach the cerebellar cortex and elicited an evoked potential. When A- and C-fiber were activated at the same time, C-CEP might be inhibited by the A-fiber input.