BACKGROUND During septic shock, the vasoconstrictor response to norepinephrine is seriously blunted. Animal experiments suggest that hyperpolarization of smooth muscle cells by opening of potassium (K) channels underlies this phenomenon. In the present study, we examined whether K-channel blockers and/or nitric oxide (NO) synthase inhibition could restore norepinephrine sensitivity during exper...

-According to the "epinephrine hypothesis," circulating epinephrine taken up by sympathetic nerves is coreleased with norepinephrine during sympathetic stimulation and binding of coreleased epinephrine to presynaptic beta-adrenoceptors augments exocytotic release of norepinephrine, contributing to high blood pressure. This study examined whether infusion of a physiologically active amount of ep...

The regulation of triglyceride mobilization by catecholamines was investigated in the teleost fish Oreochromis mossambicus (tilapia) in vivo and in vitro. In vitro experiments were carried out with adipocytes that were isolated for the first time from fish adipose tissue. For the in vivo experiments, cannulated tilapia were exposed to stepwise decreasing oxygen levels (20, 10, and 5% air satura...

Previous studies have suggested that catecholamine uptake may play a role in vascular responsiveness in hypertension. The current study was undertaken to characterize amine uptake and effects of its inhibition in an isolated human artery from normotensive subjects and to provide a basis for future study in hypertensive individuals. Accumulation of tritiated norepinephrine into the artery of nor...

BACKGROUND Despite the widespread use of tyramine as a pharmacological tool to assess the effects of norepinephrine release from sympathetic nerve terminals, its vascular effects are not adequately characterized. In particular, previous results indicate that intravenous tyramine produces little if any systemic vasoconstriction, suggesting that tyramine does not cause significant norepinephrine ...

To characterize pulmonary and total body norepinephrine and epinephrine kinetics in the immediate newborn period, the effects of desipramine were studied in six fetal lambs chronically instrumented at 133-134 days gestation (term 147 days) and delivered 1 wk later by cesarean section under spinal anesthesia. Norepinephrine and epinephrine kinetics were determined with isotope dilution methodolo...

Plasma norepinephrine concentrations are elevated in patients with decompensated cirrhosis, and correlate inversely with urinary sodium and water excretion. Increased plasma norepinephrine concentrations may result from a decreased metabolic clearance rate or an increased secretion rate, possibly in response to a decreased "effective arterial blood volume." If the latter hypothesis is correct, ...

To study the effect of fetal hypoxemia on perinatal norepinephrine and epinephrine total body kinetics, 13 near-term fetal lambs were instrumented with vascular catheters under general anesthesia. One week later, norepinephrine and epinephrine kinetics were measured in normoxemic ( n = 7) or spontaneously hypoxemic fetuses ( n = 6) with isotope dilution methodology. Hypoxemic fetuses had lower ...

PURPOSE To characterize the prejunctional mechanisms that control the impulse-evoked release of norepinephrine in the isolated, superfused human iris-ciliary body. METHODS Human iris-ciliary body tissue segments were preincubated with 3H-norepinephrine, superfused and electrically-stimulated in vitro to evoke the discharge of 3H-norepinephrine. The effects of prejunctional modulators on evoke...

The role of the sympathetic nervous system in the development of deoxycorticosterone-sodium chloride (DOCA-saline) hypertension was investigated by measuring plasma levels of norepinephrine, total catecholamines, and dopamine-beta-hydroxylase activity at intervals after the initiation of the DOCA-saline regimen. Plasma norepinephrine was significantly higher in DOCA-saline-treated rats at 4 and...