On the specification of taste neurons in the rat tongue.

It is known in mammals that regenerating taste fibers will reform, innervate and maintain new taste buds in characteristic tongue locations--the taste papillae. The ability of non-taste sensory and motor nerve fibers (auriculo-temporal, mylohyoid and hypoglossal nerves) to substitute for a taste (IXth) nerve was evaluated by whole nerve recording and anatomical examination of experimentally innervated rat tongues. The non-taste nerve endings grew into the tongue and were physiologically responsive to cooling and to localized mechanical stimulation of the foliate and circumvallate taste papillae on the tongue. However, unlike the control regenerated IXth nerve these non-taste nerves were unable to (1) reform new taste buds, or (2) innervate, and (3) maintain existing taste buds. It was suggested that taste fibers have physico-chemical properties which permit interaction with groups of specialized cells in the dorsal epithelium of the tongue (taste receptor cell precursors) by a process involving recognition between matched taste fiber and nascent receptor cell.