We tested the hypothesis that pressor infusions of angiotensin II (AII) could stimulate the sympathetic nervous system as reflected by norepinephrine (NE) spillover in humans. AII was infused at 5 ng/kg/min in six healthy volunteers, with vehicle and phenylephrine infusions as controls, on 3 separate days. Heart rate, mean arterial pressure, plasma NE, NE clearance, and NE spillover were assess...

Effect of YM-12617, a selective and potent alpha 1-adrenoceptor antagonist on dose-response curves of alpha 1-adrenoceptor agonists, norepinephrine, phenylephrine and naphazoline, was tested in isolated rabbit vascular smooth muscles such as the femoral vein, portal vein and aorta. YM-12617 shifted the dose-response curves for norepinephrine and phenylephrine to the right and also declined the ...

PURPOSE To compare the mydriatic effect and the short-term corneal endothelial safety of intracamerally injected N-methyl-3,4-dihydroxyphenylamine (epinine) to phenylephrine in a porcine eye model. METHODS One hundred twelve eyes from newly slaughtered pigs were used in this study. After pretreatment with 20 mg intracameral acetylcholine to give miosis, 0.15 mL epinine or phenylephrine 0.3%, ...

We determined the effect of alpha-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 alpha-adrenergic receptors with either phenylephrine (10(-8) M to 10(-6) M) or epinephrine (10(-8) M to 10(-6) M) plus propranolol (10(-6) M) resulted in a reduction i...

BACKGROUND Load-dependent impairment of left ventricular (LV) function was observed after leg elevation in a subgroup of coronary surgery patients. The present study investigated underlying mechanisms by comparing hemodynamic effects of an increase in LV systolic pressures with leg elevation to effects of a similar increase in systolic pressures with phenylephrine. METHODS The study was perfo...

20-HETE, a cytochrome P-450 4A (CYP4A1)-derived arachidonic acid metabolite, is a major eicosanoid formed in renal and extrarenal microcirculation. 20-HETE inhibits Ca(2+)-activated K(+) channels in vascular smooth muscle cells and thereby may modulate vascular reactivity. We transfected renal interlobar arteries with an expression plasmid containing the cDNA of CYP4A1, the low-K(m) arachidonic...

OBJECTIVE Surgical preparation and/or pulsatile arterial perfusion of saphenous vein increases the sensitivity of vein rings to calcium mobilising agonists such as phenylephrine. We have investigated the mechanism(s) underlying this effect. METHODS We have used an ex vivo flow circuit, with simulated arterial or venous flows (mean pressure 100 and 20 mmHg, respectively), to investigate the se...

OBJECTIVE Hypotension resulting from hemodilution on cardiopulmonary bypass is often treated by pressor (eg, phenylephrine) infusion. The effect of phenylephrine on cerebral blood flow (CBF) in this setting is not clear. It was hypothesized that phenylephrine might decrease CBF. MEASUREMENTS AND MAIN RESULTS Six different radioactively labeled microspheres (15 microm) were used to measure CBF...

The interaction between phenylephrine and calcium entry blockers was studied on the taenia of the guinea-pig caecum using the double sucrose gap method. Sustained hyperpolarization, relaxation and attenuation of evoked electrical and mechanical activity were induced by non-cumulative addition of phenylephrine (0.1 to 250 mumol.1-1) for 2 to 4 min. When the alpha 1-adrenoceptor agonist was appli...

PURPOSE To assess in normal and glaucomatous eyes the effect of the dopaminergic drug 2% ibopamine on visual acuity, IOP, pupil size and anterior segment geometry, compared with 10% phenylephrine and 1% tropicamide. METHODS Fifteen healthy subjects and 15 patients with primary open-angle glaucoma, aged from 40 to 70 years (mean age: 54.8 +/- 9.6), were recruited into this open prospective stu...