AJP - Regulatory, Integrative and Comparative Physiology, Vol 252, Issue 6 1143-R1151, Copyright © 1987 by American Physiological Society
Adrenal gland denervation and diving in ducks
H. J. Mangalam, D. R. Jones and A. M. Lacombe
The extreme elevation in plasma levels of free norepinephrine (NE) and free
epinephrine (EP), which occurs during forced diving of ducks (Anas
platyrhynchos), was studied before and after denervation of the adrenal
glands. In intact animals both NE and EP concentration increased by up to
two orders of magnitude in a 4-min dive but by a significantly lesser
amount if the duck breathed O2 before the dive. Denervating the adrenal
glands reduced the amounts of both catecholamines (CA) released during
dives, plasma EP decreased to 10%, and NE to 50% of values obtained before
denervation. Breathing O2 before a dive virtually eliminated CA release in
denervates, indicating that hypoxia was the important non-neural releasing
agent. Hypoxia was also the most important neural releasing agent compared
with hypercapnia, acidosis, or hypoglycemia. Adrenal denervation did not
cause significant changes in heart rate, blood pressure, arterial blood gas
tensions, pH, or plasma glucose during dives, although denervation caused
increased variation in some of these variables. In ducks CA release in
dives is largely due to decreasing arterial O2 partial pressure, and full
expression of the response is dependent on intact innervation of the
adrenal gland.
