GUSTATORY SENSITIVITIES OF THE HAMSTERS SOFT PALATE

The response properties of taste receptors distributed on the soft palate of the hamster were studied by recording integrated responses from the greater superficial petrosal (GSP) nerve. Stimuli were concentration series of sucrose, NaCl, HCl and quinine hydrochloride (QHCl), and several other 0.1 M salts and 0.5 M sugars. For comparison, integrated responses were recorded from the chorda tympani (CT) nerve in many of the same animals from which recordings were made from the GSP. Responses in each preparation were scaled relative to the phasic response to 0.1 M NaCl and were then expressed for each nerve as a proportion of the total response magnitude (TRM)-the sum of all the responses to the four concentration series. In this way, the relative response of each nerve to all of the stimuli could be evaluated. There were significant differences between the GSP and CT nerves in the responses to NaCl, QHCl and sucrose. Both the phasic and tonic responses to sucrose were larger in the GSP than in the CT, whereas the tonic responses to NaCl and QHCl were smaller. The slopes of the concentration-response functions for NaCl, HCl and sucrose were significantly different between the two nerves. The responses to 0.1 M sodium and lithium salts were significantly greater in the CT than in the GSP; whereas the 0.5 M sugars elicited responses in the GSP that were 2-3 times greater than in the CT nerve. A comparison of the relative responsiveness to 0.3 M sucrose, 0.3 M NaCl, 0.01 M QHCl, 0.01 M HCl and distilled water among the GSP, CT, glossopharyngeal (IXth) nerve and superior laryngeal nerve (SLN) indicated that the vast majority of information about sucrose and NaCl is transmitted to the brainstem by the VIIth nerve.