The neural activities of the greater superficial petrosal nerve of the rat in response to chemical stimulation of the palate

Abstract

A comparison of the integrated responses of the rat's greater superficial petrosal (GSP) and chorda tympani (CT) nerves to a number of taste stimuli was studied. The GSP nerve of the rat was very responsive to the chemical stimulation of the oral cavity. Among the selected stimuli related to the four basic taste qualities, 0.5 M sucrose produced the greatest neural response in the GSP nerve, whereas, 0.1 M NaCl produced the greatest in the CT nerve. The GSP nerve integrated response to 0.5 M sucrose solution was approximately three times as great in magnitude as that to a 0.1 M NaCl solution. The neural response magnitude of the GSP and CT nerves were as follows: GSP nerve; 0.5 M sucrose >0.02 M Na-saccharin >0.05 M citric acid >0.1 M NaCl > 0.01 M quinine-HCl. CT nerve; 0.1 M NaCl > 0.05 M citric acid > 0.02 M Na-saccharin > 0.01 M quinine-HCl >0.5 M sucrose. The response magnitudes of the GSP nerve to 0.3 M chloride salt solutions were: LiCl > CaCl2 > NaCl > NH4Cl > KCl, whereas the response magnitudes of the CT nerve to the above salts were: LiCl > NaCl > NH4Cl > CaCl2 > KCl. All 0.5 M solutions of the selected sugars (sucrose, rhamnose, galactose, lactose, fructose, α-methyl-D-glucoside, xylose, mannose, arabinose, maltose, sorbose and glucose) evoked neural responses in both GSP and CT nerves. The order of the response magnitudes of the GSP nerve to the selected sugars was similar to that of the CT nerve but the absolute magnitudes of the GSP nerve were greater.