AJP - Regulatory, Integrative and Comparative Physiology, Vol 232, Issue 5 137-R144, Copyright © 1977 by American Physiological Society
Impact of centrally applied biogenic amines upon the energy balance of fowl
P. E. Hillman, N. R. Scott and A. van Tienhoven
The impact of intraventricular injections of 100 microng of the biogenic
amines, norepinephrine or dopamine, upon the energy balance of white
leghorn hens Gallus domesticus was examined. Both drugs reduce metabolic
heat production (about 35% at 9 and 20 degrees C, and about 15% at 35
degrees C) by inhibiting shivering or by reducing activity or both. Also
the drugs inhibit the opposing thermal response, evaporative heat loss
(about 3% at 9 and 20 degrees C, and about 20% at 35 degrees C) by reducing
respiration rate. The relative balance of inhibiting these opposing
responses by the drugs results in hypothermia at 9 and 20 degrees C, and
hyperthermia or no change in body temperature at 35 degrees C. Both drugs
usually caused an initial vasodilation of the feet and comb at all
temperatures tested but did not persist long enough to have much of an
impact on body temperature. It was concluded that differing ambient
temperatures do not alter the action of the biogenic amines upon the modes
of physical thermoregulation in chickens even though the direction of body
temperature change is reversed at different ambient temperatures.
