Exogenous vasopressin reverses hyperactivity in the hypothalamus of Brattleboro rats

We have previously described an increase of cytochrome oxidase (COX) activity in discrete hypothalamic nuclei of the Brattleboro rat (BR). The present experiments were done to investigate whether this increase in COX activity could be eliminated by administration of exogenous arginine vasopressin (AVP). Continuous infusion of AVP to BR for 7 days corrected the polyuria and the urine hypoosmolality, as expected, and it also eliminated the COX hyperactivity in the paraventricular nucleus and nucleus circularis of the BR hypothalamus. These results suggest that the hyperactivity of these nuclei in the BR is directly related to their inability to produce AVP.