title: Cooling-evoked hemodynamic perturbations facilitate sympathetic activity with subsequent myogenic vascular oscillations via alpha2-adrenergic receptors.
abstract: This study extends our previous work by examining the effects of alpha2-adrenoceptors under cold stimulation involving the increase of myogenic vascular oscillations as increases of very-low-frequency and low-frequency of the blood pressure variability. Forty-eight adult male Sprague-Dawley rats were randomly divided into four groups: vehicle; yohimbine; hexamethonium+yohimbine; guanethidine+yohimbine. Systolic blood pressure, heart rate, power spectral analysis of spontaneous blood pressure and heart rate variability and spectral coherence at very-low-frequency (0.02 to 0.2 Hz), low-frequency (0.2 to 0.6 Hz), and high-frequency (0.6 to 3.0 Hz) regions were monitored using telemetry. Key findings are as follows: 1) Cooling-induced pressor response was attenuated by yohimbine and further attenuated by hexamethonium+yohimbine and guanethidine+yohimbine, 2) Cooling-induced tachycardia response of yohimbine was attenuated by hexamethonium+yohimbine and guanethidine+yohimbine, 3) Different patterns of power spectrum reaction and coherence value compared hexamethonium+yohimbine and guanethidine+yohimbine to yohimbine alone under cold stimulation. The results suggest that sympathetic activation of the postsynaptic alpha2-adrenoceptors causes vasoconstriction and heightening myogenic vascular oscillations, in turn, may increase blood flow to prevent tissue damage under stressful cooling challenge.
authors.affiliation: Division of Medical Research and Education, Cheng Hsin General Hospital, Beitou, Taipei, Taiwan. ch8388@chgh.org.tw.
authors.forename: Y-H
authors.initials: YH
authors.lastname: Lin
authors.forename: Y-P
authors.initials: YP
authors.lastname: Liu
authors.forename: Y-C
authors.initials: YC
authors.lastname: Lin
authors.forename: P-L
authors.initials: PL
authors.lastname: Lee
authors.forename: C-S
authors.initials: CS
authors.lastname: Tung
mesh_terms: D058669:Adrenergic alpha-2 Receptor Antagonists / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D003080:Cold Temperature / Q000009:adverse effects*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology*; D008297:Male; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology*; D013686:Telemetry / Q000379:methods; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D058669:Adrenergic alpha-2 Receptor Antagonists; D018341:Receptors, Adrenergic, alpha-2; D015016:Yohimbine