Abstract 14083: Central Chemoreflex Activation Induces Sympathoexcitation, Whereas Does Not Affect Dynamic or Static Baroreflex Function
BACKGROUNDS: Central chemoreflex activation induces sympathoexcitation. The augmented chemoreflex and impaired baroreflex in heart failure result in excessive sympathoexcitation and poor prognosis. However, how the central chemoreflex interacts with the baroreflex remains unknown. The aim of this study was to examine the impact of the central chemoreflex on the dynamic as well as static baroreflex function under the open-loop condition. METHODS/RESULTS: In 7 anesthetized, vagotomized SD rats, we cut the aortic depressor nerves, isolated the bilateral carotid sinuses and controlled intra-sinus pressure (CSP). We recorded sympathetic nerve activity (SNA) at the celiac ganglia. We activated the central chemoreflex by hypercapnia (inhalation of 3% CO2). Protocol 1 (Static) ; We increased CSP stepwise from 60 to 170 mmHg and measured steady-state responses of SNA (neural arc) and aortic pressure (AP) responses to SNA (peripheral arc). Hypercapnia markedly increased SNA (ΔSNA=53.4±7.1%, p<0.01) irrespective of CSP indicating the resetting of the neural arc. In contrast, the peripheral arc did not change. The total loop gain at the operating point unchanged (-1.09±0.13 vs. -1.43±0.18, p=ns). Protocol 2 (Dynamic) ;We randomly perturbed CSP with binary white noise sequences (mean AP±20mmHg). We estimated transfer functions in the frequency range between 0.01 to 1.0 Hz. The transfer function of the neural arc approximated a highpass filter, while that of the peripheral arc approximated a lowpass filter. Hypercapnia did not affect the transfer function of the neural or peripheral arcs. The dynamic gain of total baroreflex transfer function remained unchanged (-0.92±0.12 vs.-0.99±0.11, p=ns). CONCLUSION: Hypercapnia resets the baroreflex neural arc upward, while does not affect baroreflex pressure buffering function. The central chemoreflex modifies hemodynamics via sympathoexcitation without compromising the dynamic or static baroreflex function.
- © 2012 by American Heart Association, Inc.