Gradual changes in body sodium status induce a specific pattern of behavioural, renal and brain activity

MACCHIONE AF; BEAS C; VIVAS L

Foz de Iguazú

Congreso; 1st PanAmerican Congress of Physiological Sciences (PanAm),; 2014

We analyzed the effect of gradual changes in body sodium status induced by iv infusions of hypotonic (0.075M) and mild (0.3M) or high (1.5M) hypertonic sodium solutions on drinking, renal and brain activity responses. Male rats were iv infused with either of the 3 solutions or saline (0.15M) as a control (0.15ml/min/20min). For behavioural and urinary measurements, rats had access to water during the infusion period and 2h after. For immunehystochemical studies other group of rats was infused without access to water and brains were collected 60 min after the 20 min of infusion. Our results indicate that both 0.3M and 1.5M groups had a gradual increase in renal Na-excretion but only in the 1.5M group, thirst was elicit. Consistently, the telencephalic circumventricular organs (CVOs) were activated in 1.5M group while the supraoptic vasopressinergic/oxitocinergic (AVP/OT) cells were gradually activated in both, 0.3M and 1.5M groups. The 0.075M group had a different K-renal-excretion suggesting the existence of aldosterone-mediated cell-volume regulation. Our data reveals a gradual increase in body sodium status that first triggers renal response and hypothalamic AVP/OT cells activation without any drinking response. However, a higher level of sodium overload elicits thirst and activation of telencephalic CVOs.