Motor unit area in a rat muscle

¹ National Institute of Neurological Diseases and Blindness, National Institutes of Health, Bethesda, Maryland

Single motor axons to rat peroneus longus were isolated in the ventral root. The muscle was then explored with a microelectrode during stimulation of the axon. The muscle fibers supplied by the axon were identified by the intracellular depolarization potentials evoked by axon stimulation. In ten experiments the muscle fibers of a motor unit were rather widely scattered. This indicates that in certain motor units all the muscle fibers are not grouped together within one area of the muscle.