title: Spectral analysis of cooling induced hemodynamic perturbations indicates involvement of sympathetic activation and nitric oxide production in rats.
abstract: OBJECTIVE
  Oscillations in arterial pressure and heart period in response to cold stress are poorly understood. We used a telemetric device with spectral and cross-spectral analyses to assess variabilities in the heart rate (HRV) and blood pressure (BPV) of conscious rats receiving a cooling stimulus (CS) (rapid immersion of palms and soles into 4°C water) at ambient thermoneutral conditions (TC), in a cold room (CC), and when under pentobarbital anesthesia (UA).
  
  
  METHODS
  Power spectra of very low, low, and high frequencies (VLF: 0.02 to 0.2Hz, LF: 0.2 to 0.6Hz, and HF: 0.6 to 3.0Hz), dicrotic notch (Dn) and plasma nitric oxide (NO) levels were measured for statistical comparisons.
  
  
  RESULTS
  When compared to resting rats (PreCS), CS evoked in rats the following hemodynamic perturbations: 1) pressor and tachycardia; 2) increases in VLFBPV, LFBPV, HFBPV, and TPBPV but decreases in VLFHRV, LFHRV, and TPHRV; 3) a positive correlation between LFBPV and VLFBPV but an inverse correlation between VLFHRV and VLFBPV and LFHRV and LFBPV; 4) high coherence value at frequency region of LF between BPV and HRV; and 5) increase of NO production and disappearance of Dn. Additionally, CS of CC and UA rats compared with TC rats evoked different patterns of hemodynamic perturbations; CC rats were activated but UA rats were inactivated.
  
  
  CONCLUSIONS
  Our findings indicate that changes in VLFBPV are related to the myogenic vascular responsiveness to CS. Power spectra changes to CS are highly relevant to sympathetic activation and NO production.
authors.affiliation: Department of Physiology, National Defense Medical Center, Taipei, Taiwan.
authors.forename: Yia-Ping
authors.initials: YP
authors.lastname: Liu
authors.affiliation: Division of Medical Research and Education, Cheng Hsin General Hospital, Taipei, Taiwan.
authors.forename: Yi-Hsien
authors.initials: YH
authors.lastname: Lin
authors.affiliation: Department of Physiology, National Defense Medical Center, Taipei, Taiwan.
authors.forename: Yu-Chun
authors.initials: YC
authors.lastname: Chen
authors.affiliation: Department of Electrical Engineering, National Central University, Taipei, Taiwan.
authors.forename: Po-Lei
authors.initials: PL
authors.lastname: Lee
authors.affiliation: Division of Medical Research and Education, Cheng Hsin General Hospital, Taipei, Taiwan. Electronic address: ch8388@chgh.org.tw.
authors.forename: Che-Se
authors.initials: CS
authors.lastname: Tung
mesh_terms: D000818:Animals; D062186:Arterial Pressure; D058639:Cold-Shock Response; D006339:Heart Rate; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis* / Q000097:blood; D017207:Rats, Sprague-Dawley; D013057:Spectrum Analysis; D013564:Sympathetic Nervous System / Q000502:physiology*
chemical_list: D009569:Nitric Oxide
keywords: Cold stress; Myogenic vascular responsiveness; Nitric oxide; Spectral analysis; Sympathetic activation