Conditioned food aversion elicited by the temperature of drinking water as a conditioned stimulus in rats.

It is known that taste can act as a conditioned stimulus (CS) for conditioned food aversion. In the present study, in order to examine whether or not the temperature of drinking water can be a CS, we conducted behavioral experiments in Wistar rats. The following results were obtained: (1) The rats subjected to aversive conditioning to 5 or 40 degrees C distilled water could learn to avoid these CSs, but they did not avoid any taste stimuli. (2) The rats subjected to aversive conditioning to 5 or 40 degrees C 0.1 M sucrose developed a generalized avoidance to sucrose at any temperature. (3) When rats familiarized to 25 degrees C 5 mM saccharin-Na (Sacc) were subjected to aversive conditioning to 5 or 40 degrees C Sacc, they avoided the respective CS, but they did not generalize it to any other stimuli even if having the same temperature as the CS. (4) The rats which had undergone transection of the taste nerves (chorda tympani and glossopharyngeal nerves) could acquire the conditioned response to the temperature of the CS. These results suggest that rats can be conditioned to temperature aversion and that the taste nerves are not needed in the formation of this conditioning.