title: Coupling of sympathetic nerve traffic and BP at very low frequencies is mediated by large-amplitude events.
abstract: This study explores the functional association between renal sympathetic nerve traffic (NT) and arterial blood pressure (BP) in the very-low-frequency range (i.e., <0.1 Hz). NT and BP (n = 6) or BP alone (n = 17) was recorded in unanesthetized rats (n = 6). Data were collected for 2-5 h, and wavelet transforms were calculated from data epochs of up to 1 h. From these transforms, we obtained probability distributions for fluctuation amplitudes over a range of time scales. We also computed the cross-wavelet power spectrum between NT and BP to detect the occurrence in time of large-amplitude transient events that may be important in the autonomic regulation of BP. Finally, we computed a time sequence of cross correlations between NT and BP to follow the relationship between NT and BP in time. We found that NT and BP follow comparable self-similar scaling relationships (i.e., NT and BP fluctuations exhibit a certain type of power law behavior). Scaling of this nature 1) points to underlying dynamics over a wide range of scales and 2) is related to large-amplitude events that contribute to the very-low-frequency variability of NT and BP. There is a strong correlation between NT and BP during many of these transient events. These strong correlations and the uniformity in scaling imply a functional connection between these two signals at frequencies where we previously found no connection using spectral coherence.
authors.affiliation: Department of Chemistry, Asbury College, Wilmore, KY 40390-1198, USA. deburgess@asbury.edu
authors.forename: Don E
authors.initials: DE
authors.lastname: Burgess
authors.forename: David C
authors.initials: DC
authors.lastname: Randall
authors.forename: Richard O
authors.initials: RO
authors.lastname: Speakman
authors.forename: David R
authors.initials: DR
authors.lastname: Brown
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D004594:Electrophysiology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013564:Sympathetic Nervous System / Q000502:physiology*