AT1 receptor role in the hypothalamic and renal function interaction

Angiotensin II (ANG II) is involved in the renal sodium homeostasis in close relation with sympathetic nervous system (SNS) under normal and pathological conditions. Vasopressin (AVP), a hormone that modulates renal sodium and water reabsorptionis synthetized and released from supraoptic (SON) and paraventricular nucleus (PVN) under ANG II influence. We hypothesized that brain ANG II AT1 receptors (AT1-R) regulate renal sodium and water reabsorption and excretion through SNS. In this study male Wistar rats with renal denervation/sham and fed with hypersodic (4%) or normal (0.4%) diet were evaluated during 5 days in metabolic cages. On day 5 were injected in lateral ventricle with losartan (AT1-R antagonist) and sacrificed 12 hours later. The urine was daily collected, blood samples and brains were obtained for determinations. The parameters analyzed were: a) c-Fos immunoreactivity in SON, PVN, subfornical (SFO) and organum vasculosum of the lamina terminalis nucleus (OVLT), b) c-Fos-AVP immunoreactivity in SON in sham group, c) sodium and water intake, d) water, sodium and creatinine excretion. Results: c-Fos expression in SFO, OVLT and PVN was differentially affected by hypersodic diet or losartan depending on renal nerve integrity. In sham animals losartan prevented the hypersodic diet effects in water intake, c-Fos and AVP positive neurons in SON. Renal denervation modified the effect of hypersodic diet in water intake, urinary volume and creatinine excretion; losartan prevented these alterations. Food intake was similar in all groups. Our results suggest that brain AT1-R regulate renal sodium and water reabsorption through SNS in close interaction with AVP.