AJP - Regulatory, Integrative and Comparative Physiology, Vol 246, Issue 6 979-R984, Copyright © 1984 by American Physiological Society
Reflex and local thermal control of rabbit ear blood flow
M. F. Roberts and A. C. Zygmunt
We measured thermal conductance (K) of the ears of 12 New Zealand White
rabbits during periods of core heating in which mean skin temperature and
ear temperatures (Te) were controlled. Right Te was always held at 28
degrees C; left Te was 15, 20, 24, 28, 31, 33 degrees C in separate core
heating periods. Core heating was obtained by perfusing a previously
implanted intravascular heat exchanger with hot water. Blood temperature
(Tbl) was measured with a thermocouple that had been previously placed in
contact with the common carotid artery. During heating, K rose with rising
Tbl, but the relation between K and Tbl depended on Te. At high Te, K rose
rapidly in the initial stages of core heating and soon reached its maximal
value. At cool Te, K rose slowly with rising Tbl until high Tbl was
reached; then K rose rapidly to maximal values. The maximal value of K
reached at high Tbl was independent of Te. The results suggest that local
temperature affects ear blood flow by affecting the way that ear blood
vessels react to sympathetic reflex signals.
