AT1 receptor role in the hypothalamic and renal function interaction

Angiotensin II (ANG II) is involved in renal sodium homeostasis under normal and pathological conditions in close relation with the sympathetic nervous system. Vasopressin, a hormone that modulates renal sodium and water reabsorption, is synthesized and released in the supraoptic and paraventricular nucleus under the influence of ANG II. We hypothesized that brain ANG II (AT1) receptors regulate renal sodium and water reabsorption and excretion through the sympathetic nervous system. In this study, male Wistar rats with renal denervation/sham were fed a hypersodic (4%) or normal (0.4%) diet and evaluated during 5 days in metabolic cages. On day 5, they were injected in the lateral ventricle with an AT1 receptor antagonist, losartan, and sacrificed 12 h later; blood samples and brains were obtained for evaluation. The urine was collected daily. The neuronal activation was analyzed in the nucleus of the supraoptic, paraventricular, subfornical, and organum vasculosum of the lamina terminalis. Activation of vasopressin neurons was evaluated in the supraoptic nucleus. Depending on renal nerve integrity, the hypersodic diet or losartan administration differentially affected neuronal activation. In sham animals, losartan prevented the stimulatory effects induced by the hypersodic diet in water intake and the neuronal activation in vasopressin-positive neurons. Renal denervation modified the effect of the hypersodic diet on water intake, urinary volume, and creatinine excretion, and losartan administration was able to prevent these alterations. Food intake was similar in all groups. Our results suggest that brain AT1 receptors regulate renal sodium and water reabsorption through the sympathetic nervous system in close interaction with vasopressin.