The consequences of gustatory nerve transection on taste-guided licking of sucrose and maltose in the rat.

Lick responses to sucrose and maltose (0.01-1.0 M) were measured in nondeprived rats during brief-access taste trials before and after histologically confirmed gustatory neurotomy. Pronounced decreases in sugar responsiveness occurred after combined section of the chorda tympani (CT) and greater superficial petrosal nerves. The additional section of the glossopharyngeal nerve (GL) flattened the sucrose concentration-response function. Extirpation of the sublingual and submaxillary salivary glands also attenuated sugar responsiveness. Section of the CT or GL alone or in combination caused less severe or no decreases in sugar licking. There were signs of licking impairments after some of these neurotomies, but the data suggest that changes in sugar responsiveness were not solely motor in origin. Thus the 7th nerve is necessary and most likely sufficient for the maintenance of normal unconditioned appetitive responsiveness to sucrose and maltose.