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Analysis of the baroreflex in the frequency and time domain
Author(s) -
Burgess Don,
Randall David C,
Stocker Sean D
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a473-b
Subject(s) - phenylephrine , baroreceptor , medicine , blood pressure , baroreflex , amplitude , mathematics , time domain , frequency domain , cardiology , heart rate , anesthesia , mathematical analysis , physics , computer science , quantum mechanics , computer vision
We investigated the relationship between blood pressure (BP) and renal sympathetic nerve activity (RSNA) in anesthetized rats using techniques in the frequency and time domain. BP and RSNA were smpled at 10kHz, and the amplitude of RSNA was calculated by applying a Hilbert transform. To investigate the behavior of the 0.4Hz rhythm (a spectral index of SNA) and the respiration rate, the BP and RSNA amplitude time series were lowpass filtered with a cutoff frequency of 3.0Hz and re‐sampled at 10Hz. A windowed Fourier transform (WFT) of this signal was performed using a Gaussian window of 10s width. The WFT of BP revealed a variation in the 0.4Hz rhythm and respiration before and following phenyl biguanide, phenylephrine, and sodium nitroprusside (SNP). We found that SNP removes both rhythms from the reflexive increase in RSNA (n=2). To investigate the reflexive relationship between BP and RSNA in the time domain, we modeled baroreceptor firing rate as a function of the rate of change in mean BP using a system of nonlinear ordinary differential equations (Ottesen J. Math Comp Mod , 2000 31 : –173). By relating the firing rate of RSNA, we reproduced features of the experimentally measured RSNA as a function of the experimentally measured BP. Our preliminary model indicates that the transport time delay between baroreceptor firing and RSNA is roughly 0.2 s. Supported by NS39774 and AHA0630202N