AJP - Regulatory, Integrative and Comparative Physiology, Vol 253, Issue 2 222-R227, Copyright © 1987 by American Physiological Society
Cardiovascular and metabolic responses to temperature in Coluber constrictor
J. N. Stinner
The cardiovascular adjustments associated with elevated metabolic demand
caused by rising body temperature were investigated in Coluber constrictor.
From 16 to 35 degrees C, O2 consumption increased roughly ninefold.
Systemic blood flow, determined by the Fick method, increased approximately
4.5-fold and arteriovenous O2 difference increased approximately 2-fold.
Heart rate steadily increased over the temperature range examined. At the
cooler temperatures stroke volume also increased but, above approximately
25 degrees C, stroke volume declined with rising temperature. The changes
in stroke volume may result from the direct effect of temperature on
myocardial contractility. The thermal dependence of blood convection
requirement in C. constrictor is similar to changes in air convection
requirement determined in a previous study. Consequently the minute
ventilation-to-perfusion ratio appears to be independent of temperature, at
least from 20 to 35 degrees C. Systemic arterial blood pressure increases
with rising body temperature due to the rise in cardiac output, whereas
vascular resistance declines. Blood pressure in snakes disturbed by the
investigator is roughly two times higher than in resting animals at all
temperatures studied. This marked change in blood pressure suggests an
"alarm reaction" mediated by the sympathetic nervous system.
