Glossopharyngeal nerve transection reduces quinine avoidance in rats not given presurgical stimulus exposure

Behavioral studies on the effects of bilateral glossopharyngeal nerve (GL) transection on quinine responsiveness have yielded mixed results. These differences may be explained by the presence or absence of presurgical exposure with the tastant. In the present experiment we measured unconditioned licking to quinine in rats that had no exposure to quinine before surgery. Rats were water deprived and trained to lick water during 10 s trials in an automated gustometer. Next, they were divided into groups that received either GL transection or sham surgery (CON). Following recovery, the water-deprived rats were presented with seven concentrations of quinine hydrochloride (0.003-3 mM) and distilled water. The number of licks to each tastant was averaged over three days of testing. Rats with GL transection licked significantly more to the higher concentrations of quinine relative to CON rats, resulting in a 0.44 log10 unit shift in the quinine concentration-response curve. These results when considered with prior work suggest that experience before nerve transection may have a small protective effect on taste-guided behavioral responsiveness to quinine in rats.