Sympathetic activation in the development of DOCA‐salt hypertension

Abstract

Indirect evidence indicates that sympathetic activity (SNA) is increased in DOCA‐salt hypertension. Total body norepinephrine (NE) spillover provides an accurate estimate of whole‐body SNA. The purpose of this study was to assess SNA during the development of DOCA‐salt hypertension. Catheters were implanted in male rats for pressure measurements and blood sampling. Rats drank water containing 1% NaCl and 0.2% KCl. After a 7 day recovery and 3 day control period, a DOCA pellet (50 mg/kg, sc) was implanted in some rats, while others had sham surgery. NE spillover was measured following a 90 minute 3H‐NE infusion on control day 2, and days 7 and 14 after DOCA administration or sham surgery. During the control period, mean arterial pressure (MAP) was similar in sham (106 ± 4.2 mmHg) and DOCA (107 ± 4.5 mmHg) rats. MAP was higher in DOCA rats on day 7 and 14 (113 ± 7.5 and 124 ± 5.8 mmHg) than in sham rats (104 ± 2.0 and 108 ± 15.6 mmHg). However, plasma NE concentration, clearance and spillover were not different at any time in DOCA versus sham rats. To examine possible regional sympathetic activation, celiac ganglionectomy (CGX) was performed to selectively denervate the splanchnic organs. MAP was lower in CGX than in sham‐operated rats during DOCA‐salt treatment. In conclusion, global SNA is not increased during development of DOCA‐salt hypertension, but sympathetic activation may occur specifically in the splanchnic region.