Integration of autonomic and local mechanisms in regulating cardiovascular responses to heating and cooling in a reptile (Crocodylus porosus)

Seebacher, F. and Franklin, C. E. (2004) Integration of autonomic and local mechanisms in regulating cardiovascular responses to heating and cooling in a reptile (Crocodylus porosus). Journal of Comparative Physiology B-biochemical Systemic And Environmental Physiology, 174 7: 577-585. doi:10.1007/s00360-004-0446-0


Author Seebacher, F.
Franklin, C. E.
Title Integration of autonomic and local mechanisms in regulating cardiovascular responses to heating and cooling in a reptile (Crocodylus porosus)
Journal name Journal of Comparative Physiology B-biochemical Systemic And Environmental Physiology   Check publisher's open access policy
ISSN 0174-1578
Publication date 2004-01-01
Sub-type Article (original research)
DOI 10.1007/s00360-004-0446-0
Volume 174
Issue 7
Start page 577
End page 585
Total pages 9
Editor G. Heldmaier
Place of publication New York
Publisher Springer-Verlag
Language eng
Subject C1
270603 Animal Physiology - Systems
780105 Biological sciences
Abstract Reptiles change heart rate and blood flow patterns in response to heating and cooling, thereby decreasing the behavioural cost of thermoregulation. We tested the hypothesis that locally produced vasoactive substances, nitric oxide and prostaglandins, mediate the cardiovascular response of reptiles to heat. Heart rate and blood pressure were measured in eight crocodiles (Crocodylus porosus) during heating and cooling and while sequentially inhibiting nitric-oxide synthase and cyclooxygenase enzymes. Heart rate and blood pressure were significantly higher during heating than during cooling in all treatments. Power spectral density of heart rate and blood pressure increased significantly during heating and cooling compared to the preceding period of thermal equilibrium. Spectral density of heart rate in the high frequency band (0.19-0.70 Hz) was significantly greater during cooling in the saline treatment compared to when nitric-oxide synthase and cyclooxygenase enzymes were inhibited. Cross spectral analysis showed that changes in blood pressure preceded heart rate changes at low frequencies (<0.1 Hz) only. We conclude that the autonomic nervous system controls heart rate independently from blood pressure at higher frequencies while blood pressure changes determine heart rate at lower frequencies. Nitric oxide and prostaglandins do not control the characteristic heart rate hysteresis response to heat in C. porosus, although nitric oxide was important in buffering blood pressure against changes in heart rate during cooling, and inhibition caused a compensatory decrease in parasympathetic stimulation of the heart.
Keyword Physiology
Zoology
Thermoregulation
Prostaglandins
Nitric Oxide
Heart Rate
Blood Pressure
Spectral Analysis
Blood Pressure Oscillations
Power Spectral-analysis
Term Rr Interval
Heart-rate
American Alligator
Nitric-oxide
Gallotia-galloti
Pogona-barbata
Thermoregulation
System
Q-Index Code C1

 
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Created: Wed, 15 Aug 2007, 13:22:15 EST