Conditioned taste aversion in vasopressin-deficient rats (Brattleboro strain)

Brattleboro rats are homozygous for diabetes insipidus (DI), lacking the ability to synthesize vasopressin. Previous studies reported learning deficits in DI rats on passive avoidance tasks using footshock. Other studies, however, could not replicate these results. In two experiments, we studied the learning of DI and control Long Evans (LE) rats in a different avoidance paradigm: conditioned taste aversion (CTA). In the first experiment a mild CTA to saccharin was established gradually using low levels of an illness-inducing agent (lithium chloride). In the second experiment a strong CTA was established in one acquisition trial and the extinction of the conditioned aversion was followed for 12 trials. The two experiments found no differences between the DI and LE rats in either the magnitude or the rate of acquisition and extinction of the CTA. These results suggest that vasopressin is not involved in the acquisition and retention of CTA, and support previous studies indicating that vasopressin may not be involved in avoidance learning.