Journal article
Modulation of baroreflex sensitivity and spectral power of blood pressure by heat stress and aging
American journal of physiology. Heart and circulatory physiology, Vol.272(2), pp.H776-H784
02/01/1997
DOI: 10.1152/ajpheart.1997.272.2.H776
PMID: 9124438
Abstract
To investigate the effects of hyperthermia and aging on baroreceptor-heart rate reflex sensitivity (BRS), cardiovascular parameters were recorded during a progressive rise in core temperature in conscious mature and senescent Fischer 344 rats. BRS was calculated from spontaneous changes in blood pressure and interbeat interval. Low- (LF, 0.01-0.20 Hz) and mid- (MF, 0.2-0.5 Hz) frequency blood pressure power were also determined. In both age groups, hyperthermia caused an increase in blood pressure, renal resistance, and LF but no changes in renal nerve activity, whereas a tachycardia was only observed in the older rats. Increases in BRS (0.80 +/- 0.14 vs. 1.72 +/- 0.34 ms/mmHg, P < 0.05) and MF (3.10 +/- 0.55 vs. 7.81 +/- 1.89 mmHg2, P < 0.05) and a positive correlation between BRS and MF (r = 0.50, P < 0.01) were observed with heating in mature but not senescent rats. These results indicate that LF, which increased with elevated core temperature, may be modulated by thermal stimuli. The augmented BRS in the mature group may contribute to the hemodynamic adjustments that occur with hyperthermia, whereas the lack of an increase in BRS during heat stress in the senescent group suggests that baroreceptor reflex modulation is impaired with aging. The positive correlation between BRS and MF in mature rats, together with the lack of an increase in renal sympathetic nerve activity, indicates that MF may reflect the modulating influence of the efferent sympathetic portion of the baroreceptor reflex loop on arterial blood pressure rather than merely the activity of the peripheral sympathetic nervous system.
Details
- Title: Subtitle
- Modulation of baroreflex sensitivity and spectral power of blood pressure by heat stress and aging
- Creators
- Harald M Stauss - Department of Exercise Science, The University of Iowa, Iowa City52242, USADonald A Morgan - Department of Exercise Science, The University of Iowa, Iowa City52242, USAKarl E Anderson - Department of Exercise Science, The University of Iowa, Iowa City52242, USAMichael P Massett - Department of Exercise Science, The University of Iowa, Iowa City52242, USAKevin C Kregel - Department of Exercise Science, The University of Iowa, Iowa City52242, USA
- Resource Type
- Journal article
- Publication Details
- American journal of physiology. Heart and circulatory physiology, Vol.272(2), pp.H776-H784
- DOI
- 10.1152/ajpheart.1997.272.2.H776
- PMID
- 9124438
- ISSN
- 0363-6135
- eISSN
- 1522-1539
- Language
- English
- Date published
- 02/01/1997
- Academic Unit
- Radiation Oncology; Neuroscience and Pharmacology; Provost Office Administration; Health and Human Physiology
- Record Identifier
- 9984213452302771
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