BACKGROUND The vasodilatory response to intra-arterial administration of acetylcholine is reduced in patients with congestive heart failure compared with that of normal subjects. The reduced response to acetylcholine may be related to decreased endothelial release of nitric oxide, interaction with peripheral alpha-adrenergic transmission, or production of cyclooxygenase-dependent vasoconstricti...

The effects of the neurotransmitter blockers idazoxan and phentolamine on the larval settlement of three marine invertebrate species belonging to three different phyla were investigated by using in vitro concentration-response bioassays. Since neurotransmitters are known to influence metamorphic transitions in invertebrate larvae, neurotransmitter blockers were tested to evaluated their subleth...

Background. Although a-adrenergic receptors are present in both normal and failing human left ventricular myocardium and mediate a positive inotropic effect in several other species, it is not known whether stimulation of myocardial ca-adrenergic receptors exerts a positive inotropic effect or contributes to basal contractile state in vivo in humans. Methods and Results. We studied 15 patients ...

Obstructive sleep apnea causes intermittent hypoxia (IH) during sleep and is associated with dysregulation of glucose metabolism. We developed a novel model of clinically realistic IH in mice to test the hypothesis that IH causes hyperglycemia, glucose intolerance, and insulin resistance via activation of the sympathetic nervous system. Mice were exposed to acute hypoxia of graded severity (21,...

The recent use of vasodilators to improve ventricular function in acute myocardial infarction led us to investigate the effects of nitroglycerin, nitroprusside, and phentolamine on coronary collateral flow. Dogs were studied 2-4 wk after an ameroid constrictor was placed around the left anterior descending (LAD) coronary artery. Retrograde flow and peripheral coronary pressure were measured fro...

Obstructive sleep apnea (OSA) is associated with increased sympathetic nerve activity, endothelial dysfunction, and premature cardiovascular disease. To determine whether hypoxia is associated with impaired skeletal muscle vasodilation, we compared femoral artery blood flow (ultrasound) and muscle sympathetic nerve activity (peroneal microneurography) during exposure to acute systemic hypoxia (...

We determined the effect of a-adrenergic receptor stimulation on cyclic adenosine monophosphate (cyclic AMP) concentrations in isolated myocytes derived from adult rat hearts and in isolated perfused rat hearts. Activation of a-adrenergic receptors with either phenylephrine (10~ M to 10~ M) or epinephrine (10" M to 10~ M) plus propranolol (10 ' M) resulted in a reduction in cyclic AMP levels in...

Renal vein renin activity was measured by bioassay of plasma obtained from anesthetized dogs during renal arterial infusion of sympathomimetic amines, cyclic AMP, and other nucleotides. Renin secretion was calculated as the product of renal blood flow and the arterial-renal venous renin difference. Infusion of cyclic AMP significantly increased renin secretion, while administration of ATP, ADP,...

Recently interest in investigations of adrenergic agents (stimulants and inhibitors) on gastric secretion, motility, and ulceration in experimental animals has increased (1-7). Pradhan and Wingate (6) have demonstrated that phentolamine and tolazoline enhanced the spontaneous gastric secretion in dogs while phenoxybenzamine and dichloroisopro terenol showed inhibitory effects on spontaneous as ...