Age effects on passive avoidance behavior of vasopressin-deficient Brattleboros.

Experiments in which vasopressin-deficient Brattleboros were tested in a passive avoidance procedure have yielded contradictory results. Some investigators observed the passive avoidance behavior of these subjects to be inferior to that of normal controls, while others failed to observe such differences. Inspection of the literature suggested that age differences between subjects which participated in these experiments might be responsible for the discrepancy. In the present experiment, HO-DI and HE Brattleboro rats of different ages were tested in the standard passive avoidance task. Passive avoidance performance of HO-DIs was, indeed, influenced by the age of the subject at the time of testing; HO-DIs reentered the shock compartment sooner than HE at 35 days, but later than HE at 120 days. There was no difference between the two groups of subjects at 60 days. The percentage of HO-DIs which reentered the shock compartment on the post-shock trial decreased with increasing age.