Cardiovascular actions of trout urotensin ii in the conscious
trout, oncorhynchus mykiss.
Le, Jean-Claude, Mevel, Kenneth R. Olson, Daniel Conklin, David Waugh,
D. David Smith, Hubert Vaudry, and J. Michael Conlon.
Laboratoire de Neurophysiologie (E A 1798), UFR de
M[umlaut]adecine, Universit[umlaut]a de Bretagne Occidentale, 22
Avenue Camille Desmoulins, 29285 Brest Cedex, France
APStracts 3:0202R, 1996.
The central and peripheral cardiovascular effects of synthetic trout
urotensin II (UII) were investigated in the conscious rainbow trout.
Intracerebroventricular (ICV) injection of 50 pmol UII produced a
slight (+3%) but significant (P < 0.05) increase in heart rate
but had no effect on mean arterial blood pressure. ICV injection of
500 pmol UII produced a significant (P < 0.05) rise (+8 %) in
blood pressure with no change in heart rate. In contrast to the weak
pressor effect of centrally administered UII, intraarterial injection
of UII produced a dose-dependent increase in arterial blood pressure
and decrease in heart rate with significant (P < 0.05) effects
on both parameters observed at a dose of 25 pmol. Higher doses of the
peptide produced a sustained decrease in cardiac output that
accompanied the bradycardia and rise in arterial blood pressure. The
UII-induced bradycardia, but not the increase in pressure, was
abolished by pre-treatment with phentolamine. Trout UII produced a
sustained and dose-dependent contraction of isolated vascular rings
prepared from trout efferent branchial (pD2 = 8.30) and
celiacomesenteric (pD2 = 8.22) arteries but was without effects on
vascular rings from the anterior cardinal vein. The data indicate
that the pressor effect of UII in trout is mediated predominantly, if
not exclusively, by an increase in systemic vascular resistance. The
UII-induced hypertensive response does not seem to involve release of
catecholamines but the bradycardia may arise from adrenergic-mediated
activation of cardioinhibitory baroreflexes.
Received 27 July 1995; accepted in final form 14 May 1996.
APS Manuscript Number R460-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 June 96