In isolated ventricles of old (9-19 day) chick embryonic hearts made inexcitable by inactivating the fast sodium channels with either tetrodotoxin (TTX) or elevated external potassium, catecholamines induced slow electrical responses and concomitant contractions within 1-3 minutes. These slow responses had a higher threshold and propagated at a slower velocity than did the normal action potenti...

CONTEXT Diagnosis of pheochromocytoma depends on biochemical evidence of catecholamine production by the tumor. However, the best test to establish the diagnosis has not been determined. OBJECTIVE To determine the biochemical test or combination of tests that provides the best method for diagnosis of pheochromocytoma. DESIGN, SETTING, AND PARTICIPANTS Multicenter cohort study of patients te...

Moxonidine is a centrally acting, anti-hypertensive medication that exerts additional metabolic properties. It unknown whether its effects are mediated by neurotransmitters or sympathetic tone regulators, including Neuropeptide Y (NPY). In this study, we evaluated the of moxonidine administration on serum NPY in humans. Methods: Ninety individuals with mild moderate arterial hypertension requir...