AJP - Gastrointestinal and Liver Physiology, Vol 240, Issue 1 25-G31, Copyright © 1981 by American Physiological Society
Adrenergic stimulation and blockade in colonic circulation of the rhesus monkey
J. C. Kerr and K. G. Swan
Adrenergic stimulation and blockade on inferior mesenteric arterial blood
flow (Q) were measured in anesthetized rhesus monkeys. Control Q was 25 +/-
2 (mean +/- SE) ml/min; aortic and portal venous pressures were 121 +/- 5
and 6.5 +/- 1.0 mmHg. Calculated inferior mesenteric arterial resistance
was 5.10 +/- 0.42 peripheral resistance units. Norepinephrine (N), 10(-3)
to 1.0 microgram/kg intra-arterially, caused dose-dependent decreases in Q.
Epinephrine (E) increased Q at 10(-3) microgram/kg in 60% of the animals
studied and decreased Q at the higher doses (10(-2) to 1.0 microgram/kg).
Isoproterenol (I) increased Q at all four doses studied. Ten-minute
infusions of N and E (0.5 microgram x kg-1 x min-1) caused sustained
decreases, and I caused sustained increases in Q. Autoregulatory escape was
not observed. alpha-Adrenergic receptor blockade (phenoxybenzamine)
attenuated the vasoconstrictor responses to N, but did not "reverse" the
vasoconstrictor response to E (vasodilation). beta-adrenergic receptor
blockade (propranolol) attenuated the vasodilator responses to I, but did
not alter significantly the responses to E or N. These data indicate that
in the monkey colonic circulation, alpha-adrenergic receptor stimulation
causes vasoconstriction and beta-adrenergic receptor stimulation causes
vasodilation.
