Search results for "Norepinephrine"
showing 10 items of 234 documents
Effects of alterations in sympathetic nervous activity on the severity of reperfusion-induced arrhythmias in anaesthetised rats.
1987
The effects of a number of interventions influencing sympathetic nervous activity on the severity of coronary artery reperfusion-induced arrhythmias in anaesthetised rats have been examined. Noradrenaline (0.1 microgram kg-1 min-1) reduced the mortality that usually occurred as a consequence of ventricular fibrillation. Isoprenaline (5 micrograms kg-1) did not significantly affect the severity of reperfusion-induced arrhythmias, although arrhythmias occurring during the 5-min period of ischaemia were exacerbated. The alpha-adrenoceptor antagonist nicergoline (0.25 and 0.5 mg kg-1 min-1) markedly suppressed both the ventricular tachycardia and fibrillation occurring upon release of the occlu…
The effect of dopamine on the overflow of endogenous noradrenaline from the perfused rabbit heart evoked by sympathetic nerve stimulation.
1978
1. The effects of dopamine and two dopamine receptor antagonists (pimozide, flupenthixol) on the release of endogenous noradrenaline evoked by electrical stimulation of the postganglionic sympathetic nerves and their influence on cardiac performance were measured in isolated perfused rabbit hearts. 2. Dopamine 0.2μM decreased noradrenaline overflow and ventricular tension development in response to nerve stimulation. 3. Dopamine 2μM increased spontaneous noradrenaline output and tension development. The noradrenaline overflow in response to nerve stimulation was greatly enhanced. This action was only partly reversed by wash out of exogenous dopamine, indicating de novo synthesis and facilit…
The effects of methacholine and calcium deprivation on the release of the false transmitter, ?-methyladrenaline, from the isolated rabbit heart
1976
1. Anaesthetized rabbits were infused for 20 min with 85 μg · kg−1 · min−1 (±)-α-methyladrenaline. The hearts dissected 15 min after the infusion contained 1.49 μg/g α-methyladrenaline; the endogenous noradrenaline content was correspondingly decreased. 2. Hearts from α-methyladrenaline-infused animals were isolated with the right sympathetic nerves intact and perfused. Ventricular rate, right atrial and right ventricular tensions were recorded using the transverse method. 3. Electrical stimulation (10 Hz, 1 ms, 1 min) of sympathetic nerves, perfusion with the nicotinic drug, p-aminophenethyltrimethylammonium (PAPETA) or perfusion with 54 mM KCl (high K+) solution evoked an output of both α…
Sympathetic Nerve Stimulation on the perfused rat heart. Affinities of N-methylatropine and pirenzepine at pre- and postsynaptic muscarine receptors.
1982
Rat isolated hearts with the sympathetic nerves attached were perfused with (-)-3H-noradrenaline in order to label the storage vesicles of the adrenergic nerves. Release was induced either by electrical stimulation of the nerves (3 Hz, 1 min) or by perfusion with high K+ solution (54 mM). The overflow of 3H-noradrenaline and its metabolites was determined by liquid scintillation counting after separation of the compounds by column chromatography. The experimental conditions ensured a minor contribution of 3H-metabolites to the evoked total tritium overflow. The release of 3H-noradrenaline evoked by nerve stimulation or high K+ solution was decreased in the presence of the muscarinic agonist…
The effect of methacholine on noradrenaline release from the rabbit heart perfused with indometacin
1974
The experiments were undertaken in order to study the effect of inhibition of prostaglandin synthesis on the muscarinic inhibition of noradrenaline release evoked by sympathetic nerve stimulation. The right sympathetic nerves of the perfused rabbit heart were stimulated electrically. The noradrenaline output was enhanced after perfusion of the hearts with indometacin 3×10−5 M indicating blockade of the prostaglandin-mediated negative feedback control. Both in the presence and in the absence of indometacin methacholine 4×10−5 M decreased the noradrenaline output by a similar percentage. It is concluded that the muscarinic inhibition of noradrenaline release does not require the functional in…
AF-DX 116 differentiates between prejunctional muscarine receptors located on noradrenergic and cholinergic nerves.
1989
Prejunctional affinity constants of the cardioselective muscarine receptor antagonist AF-DX 116 (11-[(2-[(diethyl-amino)methyl]-1-piperidinyl)acetyl]-5,11-dihydro-6 H-pyrido [2,3-b] [1,4] benzodiazepine-6-one) were determined for muscarine autoreceptors on cholinergic nerves of the guinea-pig ileum and for heteroreceptors on noradrenergic nerves of the rat heart and guinea-pig iris. AF-DX 116 antagonized with low affinity the muscarinic inhibition induced by arecaidine propargyl ester of the stimulation-evoked [3H]acetylcholine overflow (pA2 6.74) from the guinea-pig ileum. In contrast, AF-DX 116 was more potent in antagonizing the methacholine-induced inhibition of the stimulation-evoked […
Evidence for noradrenaline and adrenaline as sympathetic transmitters in the chicken.
1975
1 The concentrations of noradrenaline and adrenaline in various organs, arterial plasma and venous outflow from isolated hearts of adult chickens have been determined. 2 The relative adrenaline concentrations (percentage of the sum of noradrenaline and adrenaline) in the heart (33%), spleen (16%) and brain (26%) were higher than those found in mammalian organs. Chemical sympathectomy by pretreatment with 6-hydroxydopamine caused a decrease of the noradrenaline and adrenaline concentrations in the heart to 20 and 23% and in the spleen to 16 and 29%, respectively. 3 Stimulation of the right sympathetic nerves, infusion of tyramine or infusion of a modified Tyrode solution containing 108mM K+ …
Fuel selection during short-term submaximal treadmill exercise in the cold is not affected by pre-exercise low-intensity shivering.
2014
Exercise and shivering rely on different metabolic pathways and consequently, fuel selection. The present study examined the effects of a pre-exercise low-intensity shivering protocol on fuel selection during submaximal exercise in a cold environment. Nine male subjects exercised 4 times for 60 min at 50% (LOW) or 70% (MOD) of their peak oxygen consumption on a motorized treadmill in a climatic chamber set at 0 °C with (SHIV) and without (CON) a pre-exercise cooling protocol, inducing low-intensity shivering. Thermal, cardiorespiratory and metabolic responses were measured every 15 min whereas blood samples were collected every 30 min to assess serum nonesterified fatty acids (NEFA), glyce…
Serum concentrations of hydroxybupropion for dose optimization of depressed patients treated with bupropion.
2014
Background Bupropion is a dopamine and norepinephrine reuptake inhibitor approved for the treatment of depression and smoking cessation. According to the recently published reviews, it is a candidate for therapeutic drug monitoring (TDM) to improve therapeutic outcomes and reduce risks of intolerability or intoxication. In practice, however, the use of TDM is limited due to the chemical instability of bupropion. This investigation sought to determine if the major, active, and chemically stable metabolite 4-hydroxybupropion is a suitable measure to guide antidepressant drug therapy with bupropion. Methods 4-Hydroxybupropion serum levels were measured using a newly developed and validated hig…
Mechanism of the cardiovascular activity of laudanosine: comparison with papaverine and other benzylisoquinolines.
1994
1. The activity of (+/-)-laudanosine, a benzyltetrahydroisoquinoline alkaloid, was investigated in pithed rats and rat isolated aorta. Its effects on [3H]-(+)-cis-diltiazem and [3H]-nitrendipine binding to rat cerebral cortical membranes, and on the different molecular forms of cyclic nucleotide phosphodiesterases (PDE) isolated from bovine aorta were investigated. 2. The dose-response curve to methoxamine (3-300 micrograms kg-1, i.v.) in normotensive pithed rats was shifted to the right by (+/-)-laudanosine, 3 and 6 mg kg-1. 3. (+/-)-Laudanosine inhibited in a concentration-dependent manner the contractile responses evoked by noradrenaline (NA 1 microM), depolarizing solution (KCl 80 mM) o…