Afferent Renal Nerves Drive Sympathoexcitation and Hypertensive Heart Failure

BACKGROUND: Sympathetic activation plays a role in heart failure (HF) development. Afferent renal nerve input may induce sympathoexcitation via the hypothalamic paraventricular nucleus (PVN), which projects to the rostral ventrolateral medulla, a center for sympathetic regulation. Central dendritic release of vasopressin from PVN neurons reportedly stimulates neighboring presympathetic neurons, causing sympathoexcitation. This study investigated whether afferent renal nerves contribute to hypertensive cardiac dysfunction and whether the afferent renal nerve-PVN axis mediates sympathoexcitation via central vasopressin using salt-loaded Dahl salt-sensitive rats, a model of hypertensive HF. METHODS: Salt loading began at 6 weeks of age, with selective afferent renal denervation and total renal denervation performed at 9 weeks in Dahl salt-sensitive rats. HF phenotypes were examined at 16 weeks, while sympathomodulation by afferent renal denervation was assessed at 12 weeks, the pre-HF phase. RESULTS: At 16 weeks, afferent renal denervation and total renal denervation similarly improved left ventricular systolic dysfunction, reduced myocardial fibrosis and related mRNA levels, and lowered plasma norepinephrine levels without reducing blood pressure in hypertensive rats. At 12 weeks, afferent renal denervation attenuated the increase in plasma norepinephrine and presympathetic neuron activity in the PVN and rostral ventrolateral medulla in hypertensive rats, while decreasing vasopressin-producing PVN neuron activity. In acute experiments, afferent renal nerve stimulation increased sympathetic outflow, but vasopressin V1a and V1b receptor blockade in the PVN suppressed this sympathoexcitation in hypertensive rats. CONCLUSIONS: Afferent renal nerve input activates the sympathetic nervous system before left ventricular systolic dysfunction and contributes to hypertensive HF, with PVN vasopressin driving this sympathoexcitation.