Lingual mechanoreceptors activated by muscle twitch

Abstract

Two groups of mechanoreceptors in the tongue have been identified by recording afferent discharges in single nerve fibers dissected from the lingual nerves of anaesthetized cats. The groups of superficially situated, rapidly adapting mechanoreceptors had faster conduction velocities than the presumed deeply situated, slowly adapting endings. Stretch of the tongue musculature did not prove to be as efficient in activating the endings as local deformation, although it was possible to excite some of the presumed deeply situated endings in this way. No mechanoreceptor fibers could be identified in filaments dissected from the hypoglossal nerves in the same experiments. Twitches of the tongue musculature produced by stimulation of the hypo-glossal nerve were able to cause discharge of superficial and presumed deeply situated inechanoreceptors during the tension change. The timing of the discharges in response to twitch was such that it could account for the delay in synaptic potentials produced in hypoglossal motoneurones when supramaximal stimuli were applied to the hypoglossal nerve. The possible significance of mechanoreceptor discharges in reflex activation of tongue motor units is discussed.