Taste aversion following backward conditioning procedures in preweanling and adult rats

Laboratory rats, 18 and 90 days old, received an intraperitoneal injection (2% body weight) of .15M lithium chloride or .9% saline 10 or 30 min before 15-min access to 12% sucrose. Additional control groups received LiCl injection followed by tap water access. Testing with a 2-bottle choice procedure revealed reliable aversion effects for both age groups at each toxicosis-flavor interval. Adult rats showed reliably greater persistence of aversion following training with the 10- than with the 30-min interval. Rat pups showed no reliable differences in aversion across training intervals. Reliably greater aversion effects occurred for adults than for pups following training at the 10-min interval. Following training at the 30-min interval a similar reliable age effect occurred on Test Trial 1; but from Trial 2 onward the magnitude of aversion was similar for pups and adult rats.