Diet‐induced obesity differentially affects baroreflex‐mediated sympathetic and parasympathetic outflow

Abstract

Diet‐induced obesity (DIO) impairs the baroreflex control of heart rate (HR), which may arise from differential influences of the sympathetic (SNS) and parasympathetic (PNS) nervous systems. To test this hypothesis, Δ mean arterial pressure (MAP) and Δ HR to 30‐sec maximal stimulation of the aortic baroreceptors (aortic depressor nerve; 20V, 100Hz) were recorded before and after muscarinic receptor blockade (MB; methscopolamine, iv bolus 500ug/kg) in inactin‐anesthetized male SD rats. Rats were fed a normal (N, 13.5% kcal fat) or high fat diet (HFD, 33% kcal fat) for 4–5 weeks. Rats fed the HFD were separated into obesity prone (OP) or resistant (OR) groups, based on the top and bottom tertile of weight gain, respectively. Baseline values did not differ between groups.As shown in the table above, Δ HR and Δ MAP were blunted in OP rats compared to N and OR rats (†p<0.05 vs OP). Removal of PNS influence with MB attenuated Δ HR and Δ MAP in N and OR rats (*p<0.05 control vs MB), which were similar to the OP rat control responses. MB had no effect on the OP group. These findings suggest that DIO impairs aortic baroreceptor activation of the PNS, but may minimally impact the SNS. Funded by AHA (Brooks) and NIH (McCully NS045553, Brooks HL088552, Andresen HL41119). Δ HR (bpm) Δ MAP (mmHg) Control MB Control MB N (n=6) −53±7† −28±4* −57±6† −47±4* OR (n=6) −45±6† −31±3* −60±5† −48±4* OP (n=6) −30±6 −28±6 −41±8 −47±4