AJP - Regulatory, Integrative and Comparative Physiology, Vol 245, Issue 6 915-R919, Copyright © 1983 by American Physiological Society
Effect of ganglionic blockade on catecholamine secretion in exercised dogfish
D. F. Opdyke, J. Bullock, N. E. Keller and K. Holmes
A brief bout of vigorous exercise results in significant increases in
plasma epinephrine (E) and norepinephrine (NE) in the dogfish, Squalus
acanthias. Since the presence of a functioning sympathetic nervous system
in dogfish is in doubt, experiments were undertaken to show whether or not
exercise-induced catecholamine (CA) secretion is under autonomic neurogenic
control. Changes in plasma E and NE in a control group of exercised fish
were compared with changes in fish exercised while under the influence of
ganglionic blockade. Ganglionic blockade was induced in dogfish by
hexamethonium infusion before exercise. CA secretion in response to a
subsequent bout of exercise was significantly reduced without impairment of
the ability of the fish to exercise. The pattern of systemic arterial
pressure response to exercise and recovery (initial decrease during
exercise followed by a prompt recovery to control level) was not
significantly altered by ganglionic blockade. It is concluded that in
dogfish some fraction of CA secretion capacity is possibly or potentially
under neurogenically related control. Apparently the fraction of CA
secretion under such control is not essential for performing exercise. The
pattern of CA secretion accompanying the events of exercise and recovery in
dogfish suggests that CA may play a more important role in recovery from
exercise than in its performance.
