The analysis of plasma kinetics of the sympathetic neurotransmitter norepinephrine can be used to estimate sympathetic nervous "activity" (integrated nerve firing rate) for the body as a whole and for individual organs. In 12 patients with cardiac failure (left ventricular ejection fraction 10% to 39%), the mean arterial plasma norepinephrine concentration was 557 +/- 68 pg/ml (mean +/- SE) com...

• Although depletion of myoeardial norepinephrine stores has been noted following the administration of guanethidine' and reserpine,the mechanism by which this depletion occurs has not been defined. The intravenous administration of guanethidine has been shown to result in a transient sympathomimetie response, and it has been suggested that this may result from the release of norepinephrine fro...

The perfused isolated rabbit ear artery was used as a vascular model to compare the constrictor responses to exogenous and endogenous norepinephrine. The aim of the study was to estimate the concentrations of norepinephrine reaching the smooth muscle of the artery during sympathetic nerve stimulation. The artery was perfused so that exogenous norepinephrine was introduced exclusively from the a...

Unilateral injection of 6-hydroxydopamine into the locus ceruleus led to long lasting depletion of norepinephrine in the ipsilateral parietal cerebral cortex of the rat up to 8 weeks after injection. The uptake of both norepinephrine and dopamine by homogenates of parietal cortex was decreased markedly on the ipsilateral, but not on the contralateral, side. The uptake of four other neurotransmi...

The effect of ouabain on exocytotic and nonexocytotic norepinephrine release was investigated in perfused rat and guinea pig hearts. The overflow of endogenous norepinephrine and its neuronal metabolite 3,4-dihydroxyphenylethyleneglycol (DOPEG) was determined by highpressure liquid chromatography. DOPEG served as the indicator of free axoplasmic norepinephrine concentrations. The overflow of th...

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 nonnotensive subjects and to provide a basis for future study in hypertensive individuals. Accumulation of tritiated norepinephrine into the artery of non...

Smolich, Joseph J., and Murray D. Esler. Total body catecholamine kinetics before and after birth in spontaneously hypoxemic fetal lambs. Am. J. Physiol. 277 (Regulatory Integrative Comp. Physiol. 46): R1313–R1320, 1999.—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...

Norepinephrine turnover was estimated in the rat heart from the rate of release of tracer H-norepinephrine and the depletion of endogenous norepinephrine after inhibition of synthesis. Cardiac norepinephrine turnover was markedly increased in chronically hypophysectomized rats. Thyroidectomy and adrenalectomy were also associated with increased cardiac norepinephrine turnover, whereas ovariecto...

The chronotropic response of right atria isolated from 5-day-cold-exposed rats to isoproterenol and norepinephrine was studied. A large increase in the sensitivity of the pacemaker to isoproterenol and a decrease in the sensitivity to norepinephrine occurred. Determination of pA2 values of propranolol and metoprolol using isoproterenol and norepinephrine as agonists and analysis of the slopes o...

To test the hypothesis that cutaneous vasoconstrictor responsiveness to exogenous norepinephrine is reduced in older compared with young subjects, dose-response relations between norepinephrine and skin blood flow were established. Seven doses of norepinephrine (1.10(-8) to 10(-2) log M) were perfused (2 microl/min) intradermally (4 min/dose) using cutaneous microdialysis (2 probes/subject). To...