Journal of neurophysiology
-
Recordings were made from convergent neurons in trigeminal nucleus caudalis of the rat. These neurons were activated by both innocuous and noxious mechanical stimuli applied to their excitatory receptive fields located on the ipsilateral part of the muzzle. Transcutaneous application of suprathreshold 2-ms square-wave electrical stimuli to the center of the excitatory field resulted in responses to C-fiber activation being observed (mean latencies 63.6 +/- 5.5 ms). ⋯ The loss of inhibitory effects was characterized by a complete disappearance of poststimulus effects, whereas inhibition observed during the application of the noxious thermal conditioning stimulus was only partially, albeit very significantly, blocked. To ascertain further the mainly crossed nature of the pathways responsible for the heterotopic inhibitory processes, the effects of lumbar commissurotomy were investigated. Again the unconditioned C-fiber responses were unaltered by this procedure, whereas the inhibitory processes, whether triggered from the left or right hindpaw, were strongly depressed in all the experiments.(ABSTRACT TRUNCATED AT 400 WORDS)