Central integration and neural control of blood pressure during the cold pressor test: a comparison between hydrochlorothiazide and aliskiren

Individuals with hypertension and sympathetic overactivity are at risk for cardiovascular events. Renin inhibitors are new while thiazide diuretics are first‐class drugs used for treatment of hypertension. The purpose of this study was to determine whether 6 months of treatment with aliskiren ( ALSK ) or hydrochlorothiazide ( HCTZ ) would alter blood pressure ( BP ) and muscle sympathetic nerve activity ( MSNA ) indices in older mild hypertensives during a cold pressor test ( CPT ). We hypothesized that the ALSK group would demonstrate a blunted response compared to HCTZ . Nineteen (9 men, 10 women) subjects performed a CPT pre‐ and post treatment where heart rate ( HR ), systolic BP ( SBP ) and diastolic BP ( DBP ), and MSNA were measured. Blood samples were withdrawn for assessment of renal‐adrenal hormones. Both medications lowered ambulatory SBP and DBP ( P  <   0.05). Direct renin tended to be higher in the ALSK group after treatment ( P  =   0.081). Aldosterone was higher in the HCTZ group after treatment ( P  <   0.001). As expected, both groups showed increases in HR , SBP , DBP , and MSNA during the CPT (all P  <   0.05). All cardiovascular and MSNA responses were similar pre‐ and post treatment in both groups (peak CPT SBP : 26 ± 10 vs. 17 ± 21 and 21 ± 20 vs. 29 ± 15 mmHg for pre vs. post for HCTZ and ALSK , respectively; peak CPT MSNA burst frequency: 13 ± 8 vs. 11 ± 11 and 11 ± 17 vs. 6 ± 13 bursts/min; all P  >   0.05). Treatment with these antihypertensive medications lowered BP but was not successful in lowering the responsiveness to the CPT .