Different Characteristics of Gustatory Responses Between the Greater Superficial Petrosal and Chorda Tympani Nerves in the Rat

Abstract

The integrated responses to gustatory stimuli applied to the soft palate were recorded from the greater superficial petrosal nerve (GSP) and were compared with those from the chorda tympani nerve (CT) innervating the anterior part of the tongue in the rat. Stimuli included various concentrations of NaCl, sucrose, HCl and quinine hydrochloride, and 0.5 M of six sugars. The inhibitory effects of amiloride on the responses to sodium salts, including various concentration of NaCl, 0.1 M sodium acetate and 0.01 M sodium saccharin, were also tested. Both the phasic and tonic responses to sugars in the GSP were significantly larger than those in the CT, whereas both responses to NaCl in the GSP were significantly smaller than those in the CT. Although amiloride at 50 microM significantly depressed the phasic and tonic responses to NaCl with a wide range of concentration in the CT, little inhibitory effect was observed in the GSP. The tonic response to sodium acetate, when dissolved in amiloride solution, was depressed to 15% of the control in the CT, and slightly but significantly depressed to 70% in the GSP. These response characteristics of the GSP may play important roles in the processing of gustatory information.

Development and maturation of taste buds of the palatal epithelium of the rat: Histological and immunohistochemical study

“…Electrophysiological observations on the gustatory stimuli of the peripheral taste fibers argued that the greater superficial petrosal nerve, which innervates the palatal taste buds, is most responsive to sweet-tasting stimuli (Nejad, 1986;Harada et al, 1997b). In support, ␣-gustducin, which is strongly implicated in the mediation of sweet-tasting substances, was strongly expressed in the palatal taste buds (Boughter et al, 1997).…”

Behavioral Discrimination between Quinine and KCl Is Dependent on Input from the Seventh Cranial Nerve: Implications for the Functional Roles of the Gustatory Nerves in Rats

“…Although all of these branches respond to all of the classes of prototypical taste compounds, they are differentially sensitive to these sapid stimuli. The chorda tympani (C T) branch of the seventh nerve, which innervates tastes buds on the anterior tongue, is noted for its sensitivity to sodium salts and acids, whereas this nerve responds poorly to sugars and alkaloids (Pfaffmann, 1955;Frank et al, 1983;Boudreau et al, 1985;Nejad, 1986;Dahl et al, 1997;Harada et al, 1997). The greater superficial petrosal branch of the seventh nerve (GSP), which innervates palatal taste buds, responds strongly to sugars but modestly to alkaloids (such as quinine) and salts (Nejad, 1986;Nejad and Beidler, 1987;Harada et al, 1997;Sollars and Hill, 1997).…”

Expression patterns of taste transduction-related proteins during development in mouse taste buds

“…1). In rats, neural responses to sucrose [10] and glutamate [11] were greater in soft plates than the fungiform papillae. In mice, the former preferably elicits taste nerve responses to salts, but the latter, bitter substances [Harada S., personal communication].…”