Behavioral discrimination between sucrose and maltose by rats depends on the gustatory input of the seventh cranial nerve. Spector, Alan C., Stacy Markison, Steven J. St. John, and Mircea Garcea. Department of Psychology, University of Florida, Gainesville, FL 32611
APStracts 3:0404R, 1996.
Although rats treat the taste of sucrose and maltose as perceptually similar, they nonetheless appear to be able to distinguish between the two sugars as suggested from prior work examining the cross -generalization of conditioned taste aversions. This study explictly tested if rats could behaviorally discriminate sucrose from maltose and examined the relative importance of the gustatory input of the seventh and ninth cranial nerves in maintaining such performance. Water-restricted rats were presurgically trained in a conditioned avoidance task to suppress licking to either sucrose or maltose and maintain licking to the other sugar. Concentration (.05, .1, .2, & .4 M) was varied to make intensity an irrelevant cue. Stimuli were randomly presented in 5 s trials during 50 min sessions. Bilateral transection of either the chorda tympani nerve (CT) or the glossopharyngeal nerve (GL) or sham surgery did not disrupt discrimination performance. In contrast, combined transection of the CT and greater superficial petrosal nerve (GSP), which collectively removes the taste input of the seventh cranial nerve, caused severe impairments in sugar discriminability. In these rats, performance was more disturbed at the lower concentrations. These findings confirm that rats can discriminate sucrose from maltose and that this capability relies heavily on the taste input of seventh cranial nerve. Although the input of the ninth cranial nerve is unnecessary, it may help sustain partial competence in this task, especially at high concentrations, in the combined absence of the CT and GSP. 

Received 11 June 1996; accepted in final form 22 October 1996.
APS Manuscript Number R332-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996