Absence of learning and memory deficits in the vasopressin-deficient rat (Brattleboro strain)

Active and passive avoidance behavior was compared between vasopressin (ADH)-deficient rats of the Brattleboro strain and normal Long-Evans rats. In retention of a passive avoidance task across three levels of footshock (0.5, 1.0 and 1.5 mA) the ADH-deficient rats exhibited a slight but overall superior passive avoidance performance. In a one-way avoidance task, diabetes insipidus (D.I.) and normal rats had closely comparable performances; whereas, in a shuttle-box avoidance task the D.I. rats made significantly more avoidance responses than the Long-Evans rats. Flinch-jump testing indicated that the D.I. rats had a small but statistically significant lowered jump threshold. These findings, which add to an increasingly conflicting literature regarding the role of ADH in learning and memory processes, indicate that ADH per se is not critical for normal learning and memory. Possibly, variations in breeding procedures for the D.I. rat have resulted in variations in behavioral reactivity which interact with learning tasks to enhance or impair performance.