Neurophysiological Recording of the Compound Muscle Action Potential for Motor Unit Number Estimation in Mice

Motor unit number estimation (MUNE) techniques estimate the number of motor units innervating a single muscle or a group of muscles. As such, MUNE techniques are commonly used to quantify the loss of motor units in disease. MUNE requires obtaining and analysing neurophysiological recordings of compound muscle action potentials (CMAPs) evoked by stimulation of a peripheral nerve. Here, we describe a neurophysiological method that allows for the generation of stimulus–response curves that are achieved through increasing incremental electrical stimulation of the right sciatic nerve of mice and recording of the CMAP in the right gastrocnemius muscle. Performing this neurophysiological technique for subsequent MUNE analysis has vast implications for determining motor unit numbers where motor unit loss is thought to occur.