Central projection of tongue muscle afferent input

Abstract

It is thought that information from deep sensations in the tongue muscle projects to the brainstem through the hypoglossal nerve. I investigated the distribution of nociceptive neurons responding to electrical stimulation of the hypoglossal afferent nerve supplying the tongue muscle in the caudal medulla oblongata and the thalamus of a cat anesthetized with urethane and chloralose, using glass capillary microelectrodes filled with 2% pontamine sky blue in 0.5 M sodium acetate. The extracellular activity of single neurons was obtained from the subnucleus reticularis ventralis (SRV), the nucleus ventralis posteromedialis proper (VPM) and nucleus ventralis posterolateralis (VPL) of the ventrobasal (VB) complex, and the nucleus centralis lateralis (CL). A majority of the SRV neurons, and some of the VB complex and CL neurons were excited by noxious and/or innocuous stimulation to the tongue muscle. This suggests that the hypoglossal nerve contains afferent nerve fibers that project the deep sensation of the tongue centrally, and that tongue muscle inputs as well as superficial inputs are conveyed to the VB complex and CL neurons. Shika Igaku (J Osaka Odontol Soc) 2002 Dec; 65(3/4 combined): 255-265.