Sensory fibers in the nerve of the jaw opening muscles and their functional property in rabbits

Abstract

In anesthetized and immobilized adult rabbits, the peripheral stump of the mylohyoid nerve innervating musculus mylohyoideus and musculus digastricus was isolated and the activity recorded from its constituent single fibers. The fibers originated from sensory receptors in the skin, muscles, or other noncutaneous structures. The cutaneous afferent fibers had receptive fields of 11 mm 2 (average value) distributed roughly in the area covering the relevant muscles. They responded readily to air-blowing, light touch, and/or pressure whereas the muscular afferent fibers responded to stretch of either of the jaw opening muscles. The latter fibers were classified into three groups: (i) low-threshold, tension-dependent, slowly adapting units; (ii) high-threshold, tension-velocity-dependent, rapidly adapting units; and (iii) “on-off” units. The physiologic significance of these sensory fibers is discussed in relation to the type of their receptors as well as to their central linkages in the brain stem.