Operant behavior and drinking suppression in vasopressin-deficient rats (Brattleboro strain).

A group of Brattleboro rats homozygous for diabetes insipidus (DI) and a group of normal Long-Evans (LE) rats were deprived of water and tested on two tasks thought to measure reinforcement strength: a progressive-ratio schedule in an operant chamber and a quinine-induced drinking-suppression task. Since water-deprived DI rats are in more severe negative water balance than LE rats, it was hypothesized that they would sustain higher ratios than LE rats on the progressive-ratio schedule and would suppress drinking at higher quinine concentrations than LE rats. It was found that DI rats responded less than LE rats on the progressive-ratio schedule and that DI rats suppressed drinking as much as LE rats at each concentration of quinine used on the drinking-suppression test. It is suggested that the reinforcement strength of water for DI rats is not higher than that for LE rats.