Jaw-muscle spindle afferent feedback to the cervical spinal cord in the rat

摘要: Putative synaptic contacts between masticatory-muscle spindle afferents and brainstem neurons which project to the cervical spinal cord were studied in rats by combining retrograde intracellular neuronal labeling. Spinal projecting retrogradely labeled via injection of horseradish peroxidase unilaterally or bilaterally into segments C2 through C5. Twenty-four hours after peroxidase, one five jaw-muscle afferent axons physiologically identified intracellularly stained with biotinamide on each side brainstem. Horseradish-peroxidase-labeled found supratrigeminal region, trigeminal principal sensory nucleus, parvicellular reticular nucleus including its alpha division, subnuclei oralis interpolaris medullary formation. Retrogradely most numerous subnucleus oralis, formation ventral part interpolaris. A small number horseradish-peroxidase-labeled also present mesencephalic caudalis. Appositions boutons dorsomedial portions interpolaris, division. frequent portion oralis. These results indicate that some orofacial proprioceptive feedback transmitted reaches directly suggests predominately relays It is hypothesized these pathways are primarily involved coordination jaw neck movement during mastication biting.