Combined, but not single, gustatory nerve transection substantially alters taste-guided licking behavior to quinine...

On the basis of electrophysiological studies, the glossopharyngeal nerve (GL) is far more responsive to quinine than the chorda tympani (CT) or greater superficial petrosal (GSP) nerves. The licking behavior of water-deprived rats to quinine (0.03-3.0 mM) and distilled water (10-s trails) was tested before and after various nerve transections. GL+CT section caused a substantial reduction in responsiveness. GSP+CT section had a moderate effect, and GL section alone produced only marginal impairments. Control, partially desalivated, and CT-sectioned rats were unaffected. Thus, the GL is not necessary for normal unconditioned taste-guided appetitive responsiveness to quinine, but the collective input from the GSP and CT is necessary and most likely sufficient. These data suggest that the quinine-evoked input of the GL and CT converge centrally.