[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.