EFFECTS OF SUPRASPINAL STIMULATION ON RENSHAW CELLS BELONGING TO EXTENSOR MOTONEURONES

Abstract

Renshaw cells in the lumbar or sacral part of the spinal cord in decerebrate or nembutalized cats were localized by capillary microelectrodes. They were identified as belonging to extensor motoneurones by antidromic stimulation of the gastro-cnemius nerve, after section of the afferent roots. By conditioning with single shocks or tetani in appropriate areas of the cerebellum or con-tralateral ventro-medial reticular formation of the brain stem, it was found possible to augment or decrease the number of impulses discharged from single Renshaw cells in response to an antidromic test shock. Spontaneous activity of these cells could not be influenced, nor was their threshold altered by supraspinal stimuli. In one cell supra-spinal control was in evidence only with orthodromic activation of the Renshaw cell. Some Renshaw cells were sensitized by a twist of the cat''s pinna. The results are interpreted as demonstrating direct control of Renshaw cells belonging to extensor motoneurones.