Search results for "norepinephrine"
showing 10 items of 234 documents
Role of endothelium in the responses to noradrenaline in normal and sensitized guinea-pig aorta
1993
1. The pharmacological reactivity of sensitized blood vessels has been less studied than that of the airways. Aorta rings were obtained from normal (non-sensitized) and actively sensitized guinea-pigs, and prepared for isometric recording of tension changes. 2. Noradrenaline (10 nM-0.1 mM), histamine (0.1 microM-0.1 mM) and KCl (10-100 mM) produced concentration-related contractions of normal tissues. Removal of endothelium resulted in a marked leftward and upward shift of the concentration-response curve for noradrenaline but it did not alter histamine- or KCl-induced responses. Pretreatment with L-NG-nitroarginine (L-NOARG, 30 microM), haemoglobin (5 microM) or ibuprofen (10 microM) enhan…
Modulatory role of magnesium on the contractile response of rat aorta to several agonists in normal and calcium-free medium.
1993
Abstract Acute withdrawal of external Mg2+ increased basal tone of rat isolated aorta incubated in the presence of Ca2+. Above normal levels of Mg2+ (1–4 Mm) inhibited basal tone while much higher levels of the divalent cation (64–256 Mm) evoked contractile responses regardless of the presence of Ca2+. Contractile responses to noradrenaline (1μm) and KCl (80 Mm) were inhibited by addition of cumulative concentrations of Mg2+. Acetylcholine-induced contractions in the presence of physiological concentrations of Mg2+ (1 Mm) decreased gradually to the basal tone, but a sustained contraction was observed in the absence of this ion. In Ca2+-free medium, acetylcholine-induced phasic responses ind…
U-46619-induced potentiation of noradrenergic constriction in the human saphenous vein: antagonism by thromboxane receptor blockade.
2001
Objective: We investigated the potentiating effect of U-46619, a synthetic analogue of thromboxane A2 (TXA2), on the adrenergic responses in human saphenous vein. Methods: Saphenous vein rings were obtained from 35 patients undergoing coronary artery bypass surgery. The rings were suspended in organ bath chambers for isometric recording of tension. Results: U-46619 (10−10–3×10−7 mol/l) produced concentration-dependent and endothelium-independent contractile responses. U-46619 (10−10 mol/l) potentiated the contractions elicited by electrical stimulation and potassium chloride, and produced leftward shifts of the concentration–response curve for noradrenaline. The TXA2 receptor antagonist SQ-…
Modulation of adrenergic contraction of dog pulmonary arteries by nitric oxide and prostacyclin.
1999
Abstract The aim of this work was to investigate the influence of endothelium-derived nitric oxide and prostaglandins on the contractile responses of isolated dog pulmonary arteries to electrical field stimulation and noradrenaline. Electrical field stimulation (1–8 Hz, 20 v, 0.25 ms duration, for 30 s) produced frequency-dependent contractions that were abolished by tetrodotoxin, guanethidine and, prazosin (all at 10−6 M). Noradrenaline induced concentration-dependent contractions with an EC50 of 1.85 × 10−6 M. The increases in tension induced by electrical stimulation and noradrenaline were of greater magnitude in arteries denuded of endothelium. In segments with endothelium, NG-nitro- l …
Nitric Oxide Opposes Myogenic Pressure Responses Predominantly in Large Arterioles In Vivo
1998
Abstract —A myogenic vasoconstriction may amplify the effects of circulating vasoconstrictors. In cremaster arterioles, the contribution of a myogenic component to the constriction on intravenous infusion of norepinephrine (NE) or angiotensin II (Ang II) was studied. Second, the role of endothelium-derived nitric oxide (NO) in the control of these myogenic constrictions and its site of action in the resistance vascular bed was investigated. In 30 anesthetized (pentobarbital) hamsters, the cremaster was prepared for intravital microscopy, and a pneumatic vessel occluder was placed around the aorta to vary blood pressure in the hindquarter of the animal. Intravenous infusion of NE (0.5 nmol/…
Contribution of both ?- and ?-adrenoceptors to the inotropic effects of catecholamines in the rabbit heart
1992
The functional role of alpha-adrenoceptors was investigated in different parts of the rabbit heart. Phenylephrine (PE) caused a marked increase in force of contraction (Fc) and a prolongation of the action potential (AP) in preparations from the left atrium and the right ventricle. The response was less pronounced in the right atrium and in the left ventricle, whereas APs of spontaneously beating sinoatrial preparations remained completely unchanged. Phentolamine as well as the diesters phorbol 12,13 dibutyrate (PDBu) or 12-O-tetradecanoyl-phorbol-13-acetate (TPA) eliminated the effects of PE. The contribution of alpha-adrenoceptors to the effects of adrenaline (Adr) and noradrenaline (NA) …
ANTI-ARRHYTHMIC EFFECT OF DEHYDROBENZPERIDOL IN DOGS
1971
SUMMARY The anti-arrhythmic activity of dehydrobenzperidol (DBP) was studied during halothane anaesthesia in dogs. Arrhythmias were provoked by single intravenous injections of catecholamines. Two groups of dogs were studied. One received norepinephrine and the odier epinephrine. The dose just sufficient to initiate arrirythmias was defined as the “threshold”. Electrocardiogram, blood pressure and heart rate were monitored. The principal findings were:— 1 The dog heart was “sensitized” to epinephrine and norepinephrine by halothane. 2 DBP did have an anti-arrhydimic action. A dose of 0.150 mg/kg roughly doubled the “threshold”. 3 DBP had significant alpha-adrenergic blocking properties. …
Dopamine-related genes and spontaneous smoking cessation in ever-heavy smokers
2011
Several studies have provided evidence for associations of polymorphisms located in and near dopamine-related genes and nicotine dependence and other smoking-related phenotypes, including pharmacogenetic interactions. Aim: The purpose of the present work was to examine the association of SNPs in the DOPA decarboxylase (DDC), dopamine receptor D2 (DRD2) and dopamine transporter (SLC6A3) genes with smoking cessation in a large retrospective study featuring approximately 900 cessation events. Materials & methods: Data originated from the enrollment questionnaire of the epidemiological ESTHER study of community-dwelling adults aged 50–74 years, conducted in the German state of Saarland bet…
Electrical responses of pineal cells to melatonin and putative transmitters
1981
The effects of microelectrophoretically applied melatonin (N-acetyl-5-methoxy-tryptamine), noradrenaline (NOR) or acetylcholine (ACH) on the electrical activity of pineal cells during both the day- and night-time were studied in urethane anesthetised guinea-pigs. A total of 288 cells were tested with melatonin, and in addition with either NOR (120 cells) or ACH (138 cells). Of the 206 cells responding to melatonin application, 139 were excited and 67 inhibited. A total of 85 cells responded to the application of NOR, 45 being excited and 40 inhibited. Responses to ACH application were observed in 75 pineal cells, 49 units being inhibited and 26 excited. It was possible to observe excitation…
Light and drug induced changes of epiphysial synaptic ribbons.
1976
In the present investigation experiments were carried out to determine whether the functionally obscure synaptic rebbons of mammalian pinealocytes can be affected by acute changes in environmental lighting and which chemical processes may be involved in their regulation. Experiments carried out in male guinea-pigs have shown that the amounts of synaptic ribbons are immediately affected by changes in the lighting pattern. Extension of the light period reduced the normally occurring increase, whereas extension of the dark period inhibited the normally occurring decrease in the amount of synaptic ribbons. Results following injections of a number of drugs known to influence pineal function (nor…