[Descending pathways mediating the effect of stimulating cerebral peduncle on the spinal nociceptive transmission in the rat].

The descending pathways for the effects of stimulation of cerebral peduncle (CP) on the nociceptive neurons of spinal cord dorsal horn were analyzed by subtotal spinal cord lesions in anesthetized rats. Inhibition was the predominant effect of CP stimulation on the C-fiber elicited nociceptive responses of dorsal horn neurons, in 30.7% of such neurons, the inhibition was preceded by some initial excitation. In most neurons the inhibitory effect was mediated by both dorsal funiculus (DF) and dorsolateral funiculus (DLF), that of DF usually predominated. It seemed that DLF played a more important role than DF. However, the excitatory effect was mediated by DF alone. Since in the rat the corticospinal tract (CST) is situated in the DF, the results suggest that cerebral cortex can modulate spinal nociceptive transmission not only by the CST, but also through a relay in some supraspinal structure(s) sending descending fibers into the DLF.