体感皮层下行冲动与C类纤维传入在小脑皮层的相互影响

INTERACTION BETWEEN DESCENDING IMPULSE OF SOMATOSENSORY CORTEX AND PERIPHERAL C-FIBER INPUT ON CEREBELLAR CORTEX

实验用猫,在氯醛糖麻醉和三碘季铵酚制动下进行。电刺激大脑皮层体感Ⅰ区(SⅠ)和隐神经C类纤维时,在小脑皮层分别出现两个诱发电位:峰潜伏期为9.9±1.6ms的SⅠ-CEP和潜伏期为140.6±10.8ms的(C-CEP)。当SⅠ-CEP在C-CEP前出现时,C-CEP受到明显抑制,并与两者出现的时间间隔有关和刺激SⅠ区的强度相关;当SⅠ-CEP与C-CEP同时出现时,两者复合易化;当SⅠ-CEP在C-CEP后出现时,SⅠ-CEP受到轻度抑制。结果表明:体感皮层下行冲动与隐神经C类纤维传入冲动在小脑皮层可以相互影响。一般是先出现的抑制后出现的,两者出现的时间间隔越短,抑制越强,两者同时出现则复合易化。体感皮层下行冲动对C-CEP的抑制比C类纤维传入冲动对SⅠ-CEP的抑制强,提示体感皮层可能参与调制小脑皮层对C类纤维传入的反应。

Experiments were performed on cats under chloralose anaesthesia and immobilized by Flaxedil. When the somatosensory cortex (SI) was stimulated with the electric pulse, a cerebellar evoked potential (SI-CEP) with latency of 9.9±1.6ms could be recorded on the cerebellar cortex. Stimulation of the peripheral C-fiber could elicit an cerebellar evoked potential (C-CEP) with latency of 140.6±10.8ms while SI-CEP appeared before C-CEP, C-CEP was inhibited obviously. The shorter the interval between SI-CEP and C-CEP was, the stronger the inhibitory effect was. In addition, the inhibitory effect was related to the intensities of stimulation of SI area. While SI-CEP and C-CEP appeared simul-taneously,they interacted facilely. While SI-CEP appeared after C-CEP,SI-CEP was inhibited slightly. The results showed that the cerebral descending impulse and the C-f iber input from saphenous nerve could interact on the cerebellar cortex. In general, the preceding input inhibited the later one and the inhibitory effect was related with the interval between SI-CEP and C-CEP, as well as the intensities of stimulating SI area. The facilitatory effect, however, could be observed when SI-CEP and C-CEP appeared at the same time. The inhibitory effect on C-CEP by the cerebral descending impulse was stronger than that on SI- CEP by C-fiber input. It was suggested that the somatosensory cortex might participate in modulating the response of cerebellar cortex to C-fiber input.