Prolonged Activation of the Baroreflex Abolishes Obesity-Induced Hypertension

Abstract

Prolonged electrical activation of the carotid baroreflex produces sustained reductions in sympathetic activity and arterial pressure in normotensive dogs. The main goal of this study was to assess the influence of prolonged baroreflex activation on arterial pressure and neurohormonal responses in 6 dogs with obesity-induced hypertension. After control measurements, the diet was supplemented with cooked beef fat for 6 weeks, whereas sodium intake was held constant. After 4 weeks of the high-fat diet, there were increments in body weight from 25.8+/-0.7 to 38.6+/-1.0 kg, mean arterial pressure from 97+/-2 to 110+/-3 mm Hg, heart rate from 67+/-3 to 91+/-4 bpm, and plasma norepinephrine concentration from 141+/-35 to 280+/-52 pg/mL. Plasma glucose and insulin concentrations were elevated, but increases in plasma renin activity during the initial weeks of the high-fat diet were not sustained. During week 5, baroreflex activation resulted in sustained reductions in mean arterial pressure, heart rate, and plasma norepinephrine concentration; at the end of week 5, these values were 87+/-2 mm Hg, 77+/-4 bpm, and 166+/-45 pg/mL, respectively. These suppressed values returned to week 4 levels during a 7-day recovery period after baroreflex activation. There were no changes in plasma glucose or insulin concentrations, or plasma renin activity during prolonged baroreflex activation. These findings indicate that baroreflex activation can chronically suppress the sympathoexcitation associated with obesity and abolish the attendant hypertension while having no effect on hyperinsulinemia or hyperglycemia.