Abstract
We examined the dynamic baroreflex characteristics of myelinated (A-fiber) and unmyelinated (C-fiber) baroreceptor central pathways in anesthetized Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). The left aortic depressor nerve was electrically stimulated with two binary white noise signals to activate either A-fibers (A-BRx) or C-fibers (C-BRx). In WKY, the central arc transfer function estimated by A-BRx showed strong derivative characteristics with the slope of the dynamic gain (Gslope) of 13.9±1.1 dB/decade. In contrast, the central arc transfer function estimated by C-BRx exhibited non-derivative characteristics with Gslope of -0.6±1.4 dB/decade. This indicates that A-fibers are involved in fast regulation while C-fibers are vital for sustained changes by the baroreflex. The Gslope of the central arc transfer functions estimated by both A-BRx (18.4±0.8 dB/decade, P<0.01) and C-BRx (8.2±0.9 dB/decade, P<0.001) were higher in SHR compared with WKY. In conclusion, the dynamic baroreflex characteristics of the C-fiber central pathway in SHR more closely resembled A-fiber central pathway characteristics than the distinctly different characteristics observed in WKY.
