Horseradish peroxidase localization of masticatory muscle motoneurons in cat

Horseradish peroxidase has been injected into individual masticatory muscles in young and adult cats in order to determine the topography of the corresponding groups of motoneurons in the motor nucleus of the Vth nerve. The results obtained show a clear dorsoventral somatotopic distribution; the superior muscles have their motoneurons located dorsally in the nucleus and the inferior muscles ventrally; the two main jaw closers, temporalis and masseter, are represented in the dorsal and central parts of the nucleus; located more ventrally are the motoneurons for the pterygoideus medialis and lateralis, the jaw closers and abductor muscles; finally motoneurons for the jaw openers, and the anterior belly of the digastricus and mylohyoideus, occupy the ventromedial part of the nucleus. All muscles have been found to be represented along the entire length of the nucleus, with the same dorsoventral layering.