Role of adrenergic neurotransmission in the Median Preoptic Nucleus in experimental hypertension

Abstract

The present study sought to determine the involvement of the adrenergic neurotransmission in the Median Preoptic Nucleus (MnPO) in arterial blood pressure (MAP) control in normotensive and spontaneously hypertensive rats (SH). Male Wistar normotensive (NT) and SH rats (250–320g) were anesthetized with urethane (1.2 g/kg, i.v.) and instrumented for recordings of MAP, aortic blood flow (ABF) and renal (RBF). The rats were fixed in a stereotaxic apparatus and made nanoinjections (100 nl) of saline (0. 15 M) and Fentolamina (6.3 mM; α‐adrenergic antagonist). Aortic vascular conductance (AVC) and renal (RVC) was calculated as the ratio ABF or RBF/MAP and expressed as percentage of baseline. The results demonstrated that adrenergic neurotransmission blocking in MnPO resulted in a decrease in MAP (−7.7 ± 1.1 mmHg, n=7), ABF (−7.3 ± 2.0% above baseline, n=5) and RBF (−7.2 ± 2.1% above baseline, n = 7) of NT rats. In SH also observed decrease in MAP (−14.3 ± 6 mmHg, n = 6) and increase in AVC (8.3 ± 3.0% above baseline, n=5) and RVC (9.6 ± 1.9% above baseline, n=6), indicating vasodilation. These results suggest the participation of MnPO in tonic regulation of blood pressure in NT and SH rats.