TACTILE-EVOKED RESPONSE OF SENSORY FIBERS IN BUCCAL AND SUBMANDIBULARREGIONS OF THE RAT

Evoked neural responses to tactile stimulation were recorded electroph ysiologically from the mechanoreceptive afferent fibers innervating th e buccal and submandibular regions of Wistar rats anesthetized with so dium thiopental. Miniature probes 200 mum in diameter were used, and d ata analysis was performed on the mechanosensitivity of responses to t actile stimulation in the areas innervated by the mental, mylohyoid, a uriculotemporal, and cervical nerves. Mechanosensitivity of each area showed a characteristic distribution of slowly adapting (SA), rapidly adapting (RA), C-fiber (CF), and hair follicle (HF) units in individua l receptive fields. The density of the SA units was high in the areas innervated by the mylohyoid and auriculotemporal nerves. The CF units were concentrated in the small dome in the area of the mylohyoid nerve and the auriculotemporal nerve, as shown by a significant response to the dynamic features of stimulation. Estimation of the current needed for tactile acuity suggests an important role of the SA fibers in the areas innervated by the auriculotemporal, mylohyoid, and cervical ner ves.