Electrophysiological and HRP studies of the direct afferent inputs from the cochlear nuclei to the tensor tympani muscle motoneurons in the cat.

The direct fiber connections from the cochlear nuclei to the tensor tympani muscle (TTM) motoneurons were investigated by means of electrophysiological and horseradish peroxidase (HRP) methods, using cats. When HRP was injected into motoneuron region of the TTM, HRP-labelled cells were found bilaterally in the dorsal cochlear nucleus (DCN) and ventral cochlear nucleus (VCN). When the electrical stimulus was applied to the cochlear nucleus, the TTM motoneurons fired spikes monosynaptically with s short latency. These histological and electrophysiological results indicate the existence of direct fiber connections from the bilateral cochlear nuclei to the TTM motoneurons.