title: Role of Efferent Sympathoadrenal Effects in Cooling-Induced Hemodynamic Perturbations in Rats: An Investigation by Spectrum Analysis.
abstract: Cold stress may produce hemodynamic perturbations but the underlying mechanisms are still not clear. Spectral analysis was used in this study to explore that sympathoadrenal activation could be involved in mechanisms of hemodynamic perturbations to cooling. Conscious rats after treatment with a control vehicle (saline) compared with withdrawal of sympathetic influences by ganglion blocker hexamethonium (HEX) or chemical sympathectomy guanethidine (GUA) were challenged by stressful cooling as acute immersing all four extremities in ice water (4 ± 2°C) for 10 min. Plasma nitric oxide (NO) and the appearance of Dichroitic notch (DN) were measured in comparison between treatment groups throughout the experimental course. Hemodynamic indices were telemetrically monitored, and variability of blood pressure and heart rate (BPV; HRV) were assessed over a range of frequencies: very-low frequency (VLF: 0.02-0.2 Hz), low frequency (LF: 0.2-0.6 Hz), high frequency (HF: 0.6-3 Hz), normalized (n)LF, nHF, ratio LF/HF of HRV (LF/HF(HRV)), and total power (TP: ≤3 Hz). Results showed that the concomitant reciprocal changes of spectral powers existed between frequencies of BPV and HRV to the stressful cooling (i.e. VLF(BPV) versus VLF(HRV), LF(BPV) versus LF(HRV), and nLF(BPV) versus nLF(HRV)) which contribute to the underlying mechanisms of sympathetic efferent influences and myogenic cardiovascular responsiveness. Furthermore, compared with the control vehicle in the stressful cooling, HEX restrained the increase of the pressor, tachycardia and VLF(BPV), except that VLF(HRV) was reduced. GUA abolished pressor, however, restrained the increase of the tachycardia, VLF(BPV) and LF(BPV). In addition, GUA reversed the downward tendency of nLF(BPV) into an upward tendency and attenuated both nLF(HRV) and LF/HF(HRV). DN was virtually undetectable after HEX management but was apparently noticeable after GUA management. Finally, the increase of plasma NO after cooling was diminished after HEX or GUA management. Taken together, these results substantiate that the spectral changes during stressful cooling are highly relevant to the efferent sympathetic rhythmicity and subsequent NO production.
authors.affiliation: Department of Physiology, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.
authors.forename: Yia-Ping
authors.initials: YP
authors.lastname: Liu
authors.affiliation: School of Medicine, National Yang-Ming University, Taipei 11221, Taiwan, Republic of China.|Division of Medical Research and Education, Cheng Hsin General Hospital, Taipei 11280, Taiwan, Republic of China.
authors.forename: Yi-Hsien
authors.initials: YH
authors.lastname: Lin
authors.affiliation: Department of Physiology, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.
authors.forename: Chen-Cheng
authors.initials: CC
authors.lastname: Lin
authors.affiliation: Department of Physiology, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.
authors.forename: Yu-Chieh
authors.initials: YC
authors.lastname: Lin
authors.affiliation: Department of Physiology, National Defense Medical Center, Taipei 11490, Taiwan, Republic of China.
authors.forename: Yu-Chun
authors.initials: YC
authors.lastname: Chen
authors.affiliation: Department of Electrical Engineering, National Central University, Taoyuan 32001, Taiwan, Republic of China.
authors.forename: Po-Lei
authors.initials: PL
authors.lastname: Lee
authors.affiliation: Division of Medical Research and Education, Cheng Hsin General Hospital, Taipei 11280, Taiwan, Republic of China.
authors.forename: Che-Se
authors.initials: CS
authors.lastname: Tung
mesh_terms: D000311:Adrenal Glands / Q000502:physiology; D000818:Animals; D003080:Cold Temperature / Q000009:adverse effects*; D004525:Efferent Pathways / Q000502:physiology; D006439:Hemodynamics; D008297:Male; D009569:Nitric Oxide / Q000097:blood; D011897:Random Allocation; D017207:Rats, Sprague-Dawley; D013057:Spectrum Analysis; D013312:Stress, Physiological; D013564:Sympathetic Nervous System / Q000502:physiology*; D013686:Telemetry
chemical_list: D009569:Nitric Oxide