Regulation of the sympathetic nervous system by nitric oxide and oxidative stress in the rostral ventrolateral medulla: 2012 Academic Conference Award from the Japanese Society of Hypertension

Sympathoexcitation has an important role in the pathogenesis of hypertension. Previous studies have demonstrated that nitric oxide (NO) and/or oxidative stress in the brain are important for the regulation of the sympathetic nervous system. We have investigated the role of NO derived from an overexpression of endothelial NO synthase (eNOS) or oxidative stress in the rostral ventrolateral medulla (RVLM), which is known as a vasomotor center in the brainstem, on the regulation of the sympathetic nervous system. Our results indicated that NO derived from an overexpression of eNOS in the RVLM caused sympathoinhibition via an increase in γ-amino butyric acid and that angiotensin II type 1 receptor (AT₁R)-induced oxidative stress in the RVLM caused sympathoexcitation. We also demonstrated that oxidative stress in the RVLM caused sympathoexcitation via interactions with NO, effects on the signal transduction or apoptosis of the astrocytes. Furthermore, several orally administered AT₁R blockers have been found to cause sympathoinhibition via a reduction in oxidative stress through the blockade of AT₁R in the RVLM of hypertensive rats. In conclusion, our studies suggest that the increase in AT₁R-induced oxidative stress and/or the decrease in NO in the RVLM mainly cause sympathoexcitation in hypertension.