AJP - Regulatory, Integrative and Comparative Physiology, Vol 239, Issue 1 57-R61, Copyright © 1980 by American Physiological Society
Effect of 5-hydroxytryptamine and acetylcholine on the energy budget of chickens
P. E. Hillman, N. R. Scott and A. van Tienhoven
Intraventricular injections of 5-hydroxytryptamine-HCl (258 nmol) or
acetylcholine-HCl (550 nmol) in the chicken caused body temperature to rise
at 35 degrees C ambient, a result of decreased evaporative heat loss due to
bradypnea. At 10 and 20 degrees C ambient, neither drug affected body
temperature. Although these drugs decreased physical activity or shivering
or both at 10 and 20 degrees C, metabolic heat production was not depressed
enough to alter body temperature significantly. Heart rate decreased
simultaneously with decreased activity at 20 degrees C. This study is the
first to inject 5-hydroxytryptamine as a salt of HCl, instead of creatinine
sulfate, as is commonly used. It is suggested that some of the differences
reported herein, compared to other studies, are due to the type of salt
used. It is postulated that either 5-hydroxytryptamine or acetylcholine,
rather than norepinephrine, may be an important neurotransmitter in the
neural pathways for thermoregulation in chickens, even though their action
on thermoregulation is minor compared with norepinephrine.
