Response of native and stimulated ollaterals to serotonin.
Lamping, Kathryn G.
Department of Internal Medicine, The Cardiovascular Center,
University of Iowa, Iowa City, IA 52242
APStracts 3:0546H, 1996.
Previous studies suggest that collaterals constrict to serotonin. The
objective of these studies was to directly measure responses of
native and stimulated collaterals 30-400 m in diameter to serotonin
and mechanisms involved in responses to serotonin. Serotonin was
suffused onto the left ventricle of dogs and microvascular diameters
measured with computer-controlled stroboscopic illumination coupled
to a microscope-video system. Stimulated collaterals and arterioles
in collateral-dependent myocardium were measured following Ameroid
constriction of the left circumflex artery. Non-collaterals and
native collaterals were examined in dogs without a constrictor.
Serotonin produced dose-dependent dilation of non-collaterals which
was decreased in native collaterals, stimulated collaterals and
vessels in collateral-dependent myocardium. Dilation to nitroprusside
was similar in all groups. Dilation to serotonin was enhanced by
inhibition of 5HT2 receptors with ketanserin and blocked by non
-selective 5HT1 and 5HT2 receptors with methiothepin. Inhibition of NO
synthase with NG-nitro-L-arginine decreased dilation to serotonin.
Thus, collaterals and arterioles in collateral-dependent myocardium
are less sensitive to the dilating effect of serotonin. Responses to
serotonin involve a balance between dilation mediated by 5HT1
receptors and constriction mediated by 5HT2 receptors.
Received 3 September 1996; accepted in final form 10 December
1996.
APS Manuscript Number H796-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996