CENTRAL INTEGRATION OF LEFT VERSUS RIGHT BARORECEPTOR AFFERENT INPUT IN FEMALE SPONTANEOUSLY HYPERTENSIVE RATS

Abstract

Objective: Neuromodulation of blood pressure using baroreflex activation therapy is an effective means to control hypertension in resistant hypertensive patients. In a genetic rat model of essential hypertension, the spontaneously hypertensive rats (SHRs); we were able to demonstrate in male rats that preferential central integration of left baroreceptor afferent input exists relative to that of the right afferents. It remains unknown whether laterality also influences baroreflex responses in female SHRs. Accordingly, the differences in cardiovascular responses triggered by stimulation of the left and right baroreceptor afferents, as assessed by direct electrical stimulation of the aortic depressor nerve (ADN), were studied in female SHRs. Design and method: Pentobarbital-anesthetized female SHRs (25–29 weeks, n = 6–8) were instrumented for left and right ADN stimulation (1–40 Hz, 0.2 ms, 0.4 mA for 20 s) and recording of mean arterial pressure (MAP), heart rate (HR) and mesenteric (MVR) and femoral (FVR) vascular resistance. Female rats were also matched for the diestrus phase of the estrus cycle. Results: Both left and right ADN stimulation resulted in frequency-dependent reductions (P < 0.001) in MAP, HR, MVR and FVR. Reflex reductions in MAP, HR, MVR and FVR were comparable for both left-sided and right-sided stimulation. Conclusions: Unlike males, female SHRs express no differential central modulation of baroreceptor afferent input as evidenced by the comparable left versus right baroreflex-mediated depressor responses. Similar depressor responses in the left versus right stimulation may have been contributed to by the lack of differences in baroreflex-driven changes in HR and vascular resistance. Clinically, targeting either the left or right aortic nerves may equally provide adequate reductions in blood pressure in female hypertensive subjects. Future studies should elucidate the mechanisms responsible for sex differences in the central processing of baroreflex between male and female SHRs.