Unimpaired maintenance of a conditioned avoidance response in the rat with diabetes insipidus

The ability to maintain a conditioned avoidance response (CAR) was studied in normal Long-Evans rats and rats of the Brattleboro strain which were either homozygous or heterozygous for hereditary hypothalamic diabetes insipidus (DI). Homozygous DI rats had a lower CAR acquisition rate than did normal or heterozygous DI rats. However, the homozygous DI rats exhibited significantly greater CAR retention than did the other animals over the total period of extinction testing. The greater CAR retention could not be accounted for by either increased sensitivity to the electric foot shock used as the unconditioned stimulus or by perching on the metal center barrier of the training shuttle box, a form of behavior unique to the homozygous DI rats. Since the homozygous DI rat is totally lacking in hypothalamic antidiuretic hormone (ADH), the greater CAR retention of these animals indicates that ADH is not a requirement for CAR retention.