AJP - Heart and Circulatory Physiology, Vol 266, Issue 2 399-H405, Copyright © 1994 by American Physiological Society
Effects of vasoactive intestinal peptide on myocardial performance
N. P. Xenopoulos and R. J. Applegate
Department of Internal Medicine, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27157.
It is now recognized that stimulation of the vagus releases both
acetylcholine (ACh) and vasoactive intestinal peptide (VIP). Whereas ACh
depresses cardiac function, recent data indicate that VIP may have a
cardiostimulatory effect. Exogenously administered VIP appears to enhance
left ventricular (LV) contractile function; however, whether endogenously
released VIP alters LV performance is not known. Accordingly, we evaluated
the effects of exogenous VIP and endogenously released VIP during vagal
stimulation after muscarinic and beta-adrenergic blockade (VS-B) on LV
performance using pressure-volume analysis. Eight anesthetized open-chest
dogs instrumented to measure LV pressure and volume (conductance catheter)
were pretreated with atropine (0.1 mg/kg) and propranolol (1 mg/kg). The
cervical vagi were transected. Hemodynamic data were obtained at steady
state and during transient vena caval occlusion. Exogenous intravenous VIP
(0.05 microgram/kg-1 x min-1) increased HR minimally [2.1 +/- 0.9%
increase; P = not significant (NS)] but significantly increased maximum
first time derivative of left ventricular pressure (dP/dtmax; 29.4 +/-
19.9% increase; P < 0.05) and the slope of the end-systolic
pressure-volume relation (Ees; 3.1 +/- 1.3 to 8.9 +/- 4.2 mmHg/ml; P <
0.05). Minimum first time derivative of left ventricular pressure
(dP/dtmin) decreased 22 +/- 16.2% (P < 0.05), and the time constant of
isovolumic relaxation (tau) decreased 38 +/- 18% (P < 0.05). During VS-B
(20 Hz, 15 v, 5 min), HR increased significantly (98 +/- 11 to 130 +/- 26
beats/min; P < 0.05). Ees also increased significantly (3.3 +/- 1.6 vs.
5.2 +/- 2.8 mmHg/ml; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
