AJP - Regulatory, Integrative and Comparative Physiology, Vol 241, Issue 3 136-R145, Copyright © 1981 by American Physiological Society
Extracerebral deep-body cold sensitivity in the Pekin duck
T. Inomoto and E. Simon
Pekin ducks, in which cerebral cold sensitivity is negligible, were
submitted to general body cooling at warm, thermoneutral, and cold ambient
temperature (Ta) with an intestinal thermode. In some animals, hypothermia
was enhanced by additional hypothalamic cooling that suppressed cold
defense. In other animals, the spinal cord was cooled, either selectively
or during intestinal cooling. From core temperature (Tc) and metabolic heat
production (M) an overall cold sensitivity of about -5 to -6 W . kg-1 .
degrees C-1 was determined at thermoneutrality. Maximum M amounted to four
to five times the resting M of 3.8 W . kg-1 and was attained when Tc fell
by 2.5 degrees C or more. In the cold, threshold Tc for the activation of M
was elevated; overall cold sensitivity remained constant. In the warmth,
threshold Tc was lowered; overall cold sensitivity was reduced, if mean
skin temperature (Tsk) remained at aout 39 degrees C or higher. Spinal cold
sensitivity amounted to about -0.25 W . kg-1 . degrees C-1 at normal Tc and
thermoneutral and warm Ta; it increased to aout -0.50 W . kg-1 . degrees
C-1 in the cold and during hypothermia. Peripheral cold sensitivity was
estimated from Tsk and M as -0.4 to -0.8 W . kg-1 . degrees C-1. It is
concluded that overall cold sensitivity in ducks mainly depends on
deep-body temperature sensors outside of the central nervous system.
