Renshaw cell discharge at the beginning of muscular contraction and its relation to the silent period

Renshaw cell activity was recorded simultaneously with the motoneuronal discharge during vibration or stretch of the triceps muscles. Both the monosynaptic reflex responses and the phasic discharge of Renshaw cells elicited by the first stroke of the vibrator or by the onset of muscle extension were followed by a period of silence in their electrical recordings. The Renshaw cell burst, recorded at the onset of both stimuli, coincided with the early part of the silent period in motoneuronal discharge. It preceded the onset of muscle contraction and ended within 30 to 40 ms after the silent period began. The silent period could still persist after the pause in the discharge of the primary endings of muscle spindles had completely disappeared. On the basis of these findings, the view that recurrent inhibition could contribute to the early part of the silent period is strongly favored.