AJP - Regulatory, Integrative and Comparative Physiology, Vol 246, Issue 3 349-R353, Copyright © 1984 by American Physiological Society
Predominantly beta-adrenergic control of equine sweating
J. Bijman and P. M. Quinton
Single equine sweat glands were found to secrete for more than 1 h in vitro
in response to pharmacologic secretagogues. The adrenergic agonists
epinephrine and norepinephrine evoked maximal sweat rates of 2.0 nl X
gland-1 X min-1. However, the concentration of norepinephrine (10(-5) M)
required to evoke the maximal response was 10 times higher than that for
epinephrine. Maximal sweat rates also were stimulated with the beta
2-adrenergic agonist terbutaline. This stimulation was blocked by the
beta-adrenergic antagonist propranolol. Moderate sweating responses were
also obtained with the alpha-adrenergic agonists phenylephrine and
methoxamine, but these responses also were blocked by propranolol. Neither
the muscarinic blocker atropine nor the alpha-adrenergic antagonist
phentolamine inhibited any of the pharmacologically induced sweat
responses. Unlike most other mammalian exocrine glands, cholinergic
agonists were ineffective in stimulating sweat secretion. Therefore equine
sweat glands apparently are under predominantly beta-adrenergic control.
