Behavioral variability within the Brattleboro and Long-Evans rat strains

Abstract

Samples of genetically diabetes insipidus (DI) and normal (NO) rats were obtained from American suppliers (Rochester (RO)/DI and NO) and from the colony maintained at Charing Cross Hospital in London (Charing Cross (CC)/DI and NO) to test the hypothesis that the behavior of vasopressin-deficient Brattleboro (DI) and possibly normal Long-Evans rats may vary significantly between different colonies. DI rats of both colonies exhibit longer latencies to emerge into an open field than do NO rats. RO/DI and CC/DI rats acquire goal-approach behavior in a straight runway at similar rates. Following shock in the runway goal box, however, RO/DI rats exhibit marked recovery of running behavior relative to CC/DI rats over the ten post-shock sessions. All DI animals show reductions in goal-approach speed on the first post-shock trial, indicating that the aversive experience is remembered. CC/NO rats acquire goal-approach behavior more slowly than RO/NO rats, but neither NO group shows substantial recovery of goal approach behavior following shock. CC/DI rats showed impaired acquisition of a delayed non-match to sample task relative to RO/DI rats. All groups demonstrated the ability to utilize representational memory to solve the delayed non-match to sample problem once the contingency was learned. The results indicate that DI and normal Long-Evans rats from different colonies show marked differences in behavior. Since differences between DI and normal rats on tests indicating memory are not consistent across colonies, it is unlikely that vasopressin deficit is solely responsible for memory deficiencies. However, vasopressin deficiency may result in changes in temperament.