Food Restriction Reduces Sympathetic Support of Blood Pressure in Spontaneously Hypertensive Rats , ,

Abstract

We tested the hypothesis that food restriction would attenuate the development of hypertension in spontaneously hypertensive rats (SHR). Furthermore, we hypothesized that food restriction would reduce the tonic sympathetic nervous system support of blood pressure in the SHR. Male SHR (Charles River, age 5 wk) were randomly assigned to ad libitum (ADLIB, n = 8) or food-restricted (FR, n = 9) groups. ADLIB rats were given free access to nonpurified diet and demineralized water. Food-restricted rats ate 60% of the amount of nonpurified diet consumed by rats in the ADLIB group. After 8 wk of treatment, ADLIB rats were heavier than FR rats (ADLIB = 318 ± 4 g; FR = 193 ± 5 g, P < 0.05). Blood pressure and heart rate (HR) were measured after chronic implantation of iliac arterial and jugular venous catheters. Food-restricted rats had lower mean arterial blood pressure (MAP) than ADLIB rats, measured in conscious, unrestrained state 4–6 h after catheterization (ADLIB = 162 ± 3 mmHg; FR = 142 ± 3 mmHg, P < 0.05) and measured on the day after surgery (ADLIB = 150 ± 6 mmHg; FR = 130 ± 3 mmHg, P < 0.05). There were no significant differences in resting HR on either day. Food-restricted rats exhibited augmented cardiac baroreflex-mediated bradycardia (bolus phenylephrine, 0.5–4.0 μg/kg intravenously) as assessed by linear slope of the ΔHR/ΔMAP relationship (ADLIB = −0.73 beats/(min⋅mmHg); FR = −1.62 beats/(min⋅mmHg), P < 0.05). Sympathetic support of blood pressure quantified by the depressor response to ganglionic blockade (hexamethonium 30 mg/kg; atropine 0.1 mg/kg intravenously), was greater in the ADLIB group (ADLIB: −59 ± 8 mmHg; FR: −36 ± 2 mmHg, P < 0.05). The results support the hypotheses that chronic food restriction reduces the development of hypertension and sympathetic support of MAP in spontaneously hypertensive rats.