Paraventricular Nucleus Regulation of Blood Pressure in Two-kidney One-clip Rats: Effects of Exercise Training and Resting Blood Pressure
AJP Regulatory Integrative and Comparative Physiology
Published online on October 02, 2013
Abstract
Exercise-induced changes in -aminobutyric acid (GABA) or nitric oxide signaling within paraventricular nucleus (PVN) have not been studied in renovascular hypertension. We tested whether exercise training decreases mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) in two-kidney one-clip hypertensive rats due to enhanced nitric oxide or GABA signaling within PVN. Conscious, unrestrained male Sprague Dawley rats with either sham (Sham) or right renal artery clipping (2K-1C) were assigned to sedentary (SED) or voluntary wheel running (ExT) for 6 or 12 weeks. MAP and angiotensin II (Ang II) were elevated in 2K-1C SED rats. The 2K-1C ExT rats displayed lower MAP at 6 weeks that did not decline further by 12 weeks. Ang II was lower in 2K-1C ExT rats. Increases in MAP, heart rate, and RSNA to blockade of PVN nitric oxide in 2K-1C SED rats were attenuated compared with either Sham group. Exercise training restored the responses in 2K-1C ExT rats. The increase in MAP in response to bicuculline was inversely correlated with baseline MAP. The rise in MAP was lower in 2K-1C SED vs either Sham group, and was normalized in the 2K-1C ExT rats. Paradoxically, heart rate and RSNA responses were not diminished in 2K-1C SED rats but were significantly lower in the 2K-1C ExT rats. Thus, the decrease in arterial pressure in 2K-1C hypertension associated with exercise training is likely due to diminished excitatory inputs to PVN because of lower Ang II and higher nitritergic tone rather than enhanced GABA inhibition of sympathetic output.