The role of endogenous opioids in congestive heart failure: effects of nalmefene on systemic and regional hemodynamics in dogs.

Abstract

We studied the role of endogenous opiates and their interrelationships with the sympathetic nervous system in an experimental preparation of right-sided congestive heart failure (CHF) produced by surgical tricuspid avulsion and progressive pulmonary arterial constriction. Three groups of dogs with CHF and one group of sham-operated dogs were studied. One group of dogs with CHF was given normal saline as pretreatment, while the other two groups were pretreated with either propranolol alone (beta-blockade) or propranolol plus prazosin (alpha- plus beta-blockade). CHF was characterized by weight gain, ascites, elevated right atrial pressure, tachycardia, and reduced cardiac output. Compared with sham-operated animals, animals with CHF exhibited significantly higher baseline levels of plasma beta-endorphin and cortisol. Furthermore, only the animals with CHF responded to the opiate receptor-antagonist nalmefene with significant increases in plasma beta-endorphin, cortisol, and adrenocorticotropic hormone. Administration of nalmefene increased aortic blood pressure, cardiac output, left ventricular dP/dt and dP/dt/P, and blood flow to the myocardium, skeletal muscle, and kidneys in dogs with CHF, but had no appreciable effects in sham-operated dogs. beta-Receptor blockade abolished the increase in cardiac output, left ventricular performance, and blood flow produced by nalmefene, but had no effect on the pressor response to nalmefene. The increase in mean aortic pressure in the beta-blockade group was accompanied by an increase in skeletal muscle vascular resistance. Addition of prazosin in the alpha- plus beta-blockade group abolished the increases in mean aortic pressure and skeletal muscle vascular resistance, suggesting that the changes after propranolol probably resulted from unmasking of alpha-receptor-mediated vasoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)