Renal Denervation by Radiofrequency Ablation Attenuates Startle Responses Selectively in Rats with Exaggerated Stress Responsiveness

Abstract

Renal denervation (RDN) is reported to reduce arterial pressure (AP) in some patients with resistant hypertension. Patients prone to develop hypertension have been reported to have greater pressor responses to stress. We hypothesized that RDN would selectively reduce hemodynamic responses to startle in those individuals who have greater responsiveness to stress. We instrumented Sprague‐Dawley rats for determination of ascending aortic blood flow using Doppler flowmetry (cardiac output) and for direct measurement of AP. After recovery, rats were tested with air jet (1 sec) and with cold water stress (60 sec) while recording hemodynamic responses. After characterizing responses to the initial startle using both stressors, RDN was performed by radiofrequency ablation (<1mW, 20 s) applied externally to each renal artery 4 times each using an RF generator (100 KHz). One week later, rats were retested for stress responsiveness. Rats were divided into those with greater or lesser AP responses to acute startle according to their initial response averages. Those rats with greater AP responses had significant reductions in the AP response and the increase in systemic vascular resistance to startle after RDN. Startle responses in rats with smaller pressor responses were not affected by RDN. These results suggest that a subset of hyper‐responders to stress may be “normalized” with RDN. Since many have proposed that some individuals develop essential hypertension due to greater stress responsiveness, these results suggest a means by which RDN might be effective in reducing arterial pressure in a subset of the population with hypertension. Supported by St. Louis University.