Baroreceptor sensitivity in diabetic rats with treated anduntreated hypertension

Background: Diabetes is associated with raised blood pressure (BP) and cardiovascular risk. Baroreceptor sensitivity (BRS) is a feedback mechanism controlling spontaneous changes in BP and decreases with age and in different diseases. Aim: To quantify BRS through spontaneous changes in BP in diabetic rats and rats treated with antihypertensive therapy. Methods: Male Wistar rats (aged 6 weeks) were divided into control (n=6), control with antihypertensive treatment (control+Tx, telmisartan, 10 mg/kg/day; n=5), induced diabetes (intraperitoneal streptozotocin, 50 mg/kg, confirmed by blood glucose measurement, n=8), and diabetes with antihypertensive treatment (diabetes+Tx; n=8). At 18 weeks, rats were anesthetized (urethane, 1.3 g/kg) and an electrocardiogram performed and aortic BP was measured (1.2 F solid-state pressure tipped catheter, introduced via the femoral artery). BRS was quantified using custom-written scripts to detect sequences of at least 3 pulses with a minimum systolic BP change of 1 mmHg and minimum R-R change of 1 ms. Results: Both control (142±16 mmHg) and diabetic (132±22 mmHg) rats were hypertensive. Anti-hypertensive treatment successfully lowered systolic BP (control+Tx 105±11 mmHg; diabetes+Tx 119±14 mmHg). Antihypertensive treatment did not alter BRS for either controls (0.87±0.45 ms/mmHg vs. control+Tx 0.88±0.33 ms/mmHg; P=0.95) or diabetic rats (diabetes 1.25±0.29 ms/mmHg vs. diabetes+Tx 1.48±1.04 ms/mmHg; P=0.56). There was also no difference between diabetic rats and controls (P=0.08) or those with antihypertensive treatment (P=0.25). Conclusions: Despite altering BP through antihypertensive treatment, BRS measured through spontaneous changes in BP, was unchanged for both control and diabetic animals.