Static input-output relations in the spinal recurrent inhibitory pathway.
The static discharge rate of Renshaw cells (studied in deafferented, intercollicularly decerebrate cats) has a nonlinear dependence on the frequency of trains of stimulus impulses to alpha-motor axons in the ventral root. This dependence is well described by a rectangular hyperbola that approaches saturation with increasing stimulus frequency. The tendency to saturate is independent of the number of motor axons exciting a Renshaw cell. On average, the stimulus frequency at which the discharge rate reaches half its saturation value lies between 10 and 15 Hz. The effect of Renshaw cell activity -- measured as the antidromic inhibition of individual alpha-motoneurons -- reflects the forms of the static frequency characteristics. An electric circuit analog of the Renshaw cell membrane is presented which serves to explain the qualitative features of the static input-output relations; the nonlinearity is the result of synapses with linear properties acting together at the cell membrane.
D000818:Animals; D002415:Cats; D004558:Electric Stimulation; D004594:Electrophysiology; D005071:Evoked Potentials; D008959:Models, Neurological; D009046:Motor Neurons / Q000502:physiology*; D009433:Neural Inhibition; D009434:Neural Pathways; D013126:Spinal Nerve Roots / Q000502:physiology*