Effects of gustatory deafferentation on ingestion of taste solutions as seen by licking behavior in rats.

The role of the taste nerves in licking behavior to various taste solutions was examined in rats. The study consisted of two experiments. In the electrophysiological experiment, the whole nerve recording of the anterior palatine nerve (PN) was performed to examine the response properties of this nerve to taste stimulation applied to the taste buds in the nasoincisal duct. When the moderate concentrations of solutions were used, the PN responded best to HCl, followed by sucrose and NaCl. Quinine hydrochloride elicited the smallest response. In the behavioral experiment, the number of licks/20 sec was measured for each of the test solutions such as 0.5 M sucrose, 0.01-1.0 M NaCl, 0.03 M HCl and 0.0005 M-0.01 M quinine in normal control and experimental rats. The experimental animals received bilateral deafferentation of the PN, chorda tympani (CT) and glossopharyngeal nerve (GN) alone or in various combinations. Rats without one of the 3 taste nerves still rejected the aversive HCl and quinine solutions. However, after lesions of both CT and GN, or all the 3 taste nerves, the rats showed a significant increase in the number of licks to these aversive solutions. These results suggest that taste aversion disappears after denervation of more than 80% of the total taste buds. The interlick interval, lick duration and the amount of intake per lick did not change significantly after sections of the taste nerves in any combinations.