Involvement of the Median Preoptic Nucleus in the arterial blood pressure regulation

Abstract

Studies have been shown that Median Preoptic Nucleus (MnPO) neurons have a great influence in the cardiovascular responses induced by changes in circulating volume. The present study sought to determine the participation of MnPO in the cardiovascular control. Male Wistar normotensive (NT) and spontaneously hypertensive (SH) rats (280–320g) were anesthetized with urethane (1.2 g/kg, i.v.) and instrumented for mean arterial blood pressure (MAP) and renal blood flow (RBF) recordings. Renal vascular conductance (RVC) was calculated as the ratio RBF/MAP and expressed as percentage of baseline. In NT rats (n=7), inhibition of MnPO nucleus produced a significant hypotension (−7 ± 1.5 mmHg) and renal vasodilation (5.3 ± 1.2% above baseline). In SH rats (n=8), hypotension response was significantly greater (−15 ± 2.7 mmHg, p<0.05) than NT rats. We also observed an increase of RVC (8.4 ± 2.4% above baseline) in HT rats. Analysis of the spread of dye nanoinjected at the end of the experiment showed that the drug injection sites were confined to the MnPO. We conclude that the MnPO nucleus is involved in the tonic regulation of blood pressure in NT rats. Moreover, the increase of neuronal activity in the MnPO may contribute to sympathoexcitation and maintenance of hypertension in SH rats. Supported by CNPq (477832/2010‐5; GRP).