Behavioral characteristics of Roman high avoidance rats homozygous for diabetes insipidus (RHA: di/di)

These experiments studied the behavior of an inbred strain of vasopressin-deficient rat, the Roman high avoidance rat homozygous for diabetes insipidus (RHA: di/di). The RHA: di/di rat has been bred to be congenic with the parent normal Roman high avoidance (RHA: +/+) strain, differing from it only by the gene(s) coding for diabetes insipidus. Therefore, the RHA: +/+ strain represents an improved model system with which to study the behavioral effects of vasopressin-deficiency, given recent findings suggesting that considerable behavioral variation exists within the Long-Evans derived Brattleboro strain of vasopressin-deficient rat. We examined the behavior of RHA: di/di and RHA: +/+ rats in the open field and on tests of approach-avoidance, spatial memory and passive avoidance. RHA: di/di rats showed retarded habituation of ambulation and elevated incidence of rearing, defecation, and ambulation in the central area of the open field, relative to RHA: +/+ rats. The RHA: di/di and RHA: +/+ rat did not differ on measures of adaptation to a novel straight runway and both groups increased latencies to enter the goal box of the runway following shock, indicating memory. RHA: di/di rats did exhibit substantial recovery of goal-approach following shock, whereas RHA: +/+ rats did not. Both groups were able to solve a delayed non-match to sample task to receive reward. RHA: di/di rats showed a slower acquisition of the contingency and significantly faster run times of choice trials of the paired run procedure. No differences were evident between groups in memory of passive avoidance. The results of these experiments suggest that hereditary deficiency of vasopressin may influence physiological processes which determine arousal or attentiveness. The effects of vasopressin deficiency on performance of memory-indicating tasks appears to be secondary to modulations in arousal.