NEUROPEPTIDH Y (NPY) PARTICIPATES IN THE CARDIOVASCU- LAR REGULATION IN THE NEWBORN LAMB

Abstract

NPY, a 36 aminoacid peptide, is one of the most active vasocon-trictor agents in the systemic and pulmonary circulation. NPY plasma concentration in adults increases during stress. Human newborns have high plasma NPY concentrations, but it is unknown whether it participates as mediator of the cardiovascular response to stress in the neonatal period. We measured cardiac output (radiactive microspheres) and aortic and pulmonary artery blood pressures and calculated systemic and pulmonary vascular resistances in 6 newborn lambs (22.8±2.9 days) before and during NPY administration, placing catheters in the pulmonary artery, descending aorta, left ventricle and inferior vena cava. A bolus of 4 nM/kg of NPY followed by an infusion of 0.2 nM/min × kg for 30 min was given 1 or 2 days after surgery after a basal period of 20 min. Aortic and pulmonary blood pressures were registered continously and cardiac output was measured at 0 min, 15 and 30 min during NPY infusion. The results were (X̄±SEM; *p>0.05, Friedman test):

NPY increased systemic and pulmonary vascular resistance. These changes along with the possible decrease of coronary blood flow could explain the fall in cardiac output. This will results in a decrease in pulmonary and systemic perfusion. These results suggest that NPY could be a mediator in the blood flow redistribution observed during stress. If its action become exagered, failure of some of the compensatory cardiorespiratory mechanisms during stress in the neonatal period can occur causing the death of the newborn.

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