Hemodynamic consequences of neuropeptide Y-induced obesity

BACKGROUND: Acute central nervous system administration of neuropeptide Y (NPY) elicits variable hemodynamic responses. Chronic intracerebroventricular (ICV) administration of NPY produces obesity in rats. Obesity has been shown to increase arterial pressure. METHODS: In this study we examined the chronic hemodynamic effects of NPY-induced obesity. Sprague-Dawley rats were implanted with radiotelemetry transmitters to continuously record heart rate and arterial pressure in the conscious state. Neuropeptide Y or vehicle was delivered into the third cerebral ventricle by osmotic minipumps over 2 weeks. Three groups were studied: vehicle, NPY-treated (free-fed), and NPY-treated (pair-fed to vehicle-treated rats). RESULTS: Neuropeptide Y increased food intake and body weight in free-fed animals, and substantially augmented visceral adiposity in both free- and pair-fed rats. Despite increased adiposity, chronic ICV administration of NPY in conscious unstressed rats did not increase arterial pressure. Neuropeptide Y decreased heart rate, suggesting a sympathoinhibitory effect. CONCLUSIONS: Obesity induced by 2-week ICV administration of NPY does not increase arterial pressure, perhaps indicating inhibition of sympathetic outflow that may oppose the pressor effect of adiposity.