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Query: UMLS:C1323099 (sympathomimetic)
 2,957 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1 The effects of some sympathomimetic amines and of carbachol and potassium chloride upon the contractility of epididymal halves of the rat vas deferens have been examined in vitro at several times following vasectomy by medial transection of the vas deferens in vivo. The inhibitory effects of noradrenaline and the excitatory effects of potassium chloride upon prostatic halves of transected tissues were also studied. 2 Partially denervated epididymal segments, taken 2 days after surgery, were spontaneously active, and responses to KCl (80 mmol/l) and maximum responses to phenylephrine were enhanced. These effects were not observed with preparations taken at later times. Spontaneous activity and enhancement of responses to KCl were abolished by guanethidine (0.1 mumol/l). 3 Supersensitivity to noradrenaline was observed in fully denervated epididymal halves of vasa deferentia taken 7-183 days after transection. The supersensitivity consisted of a leftward shift in the log concentration-response curves for noradrenaline constructed upon operated, relative to those obtained upon unoperated preparations. Supersensitivity to phenylephrine but not to methoxamine or to carbachol was also evident. 4 The magnitude of the leftward shift in the log concentration-response curve for noradrenaline in operated epididymal segments approached that produced, in unoperated segments, by nisoxetine (0.1 mumol/l). This inhibitor of neuronal uptake did not enhance the potency of noradrenaline in operated segments. 5 Prazosin (50 nmol/l) antagonized the effect of phenylephrine upon both operated and unoperated epididymal segments. The antagonism was significantly greater upon operated segments than upon unoperated segments 4 and 28 days after surgery. 6 In prostatic segments, noradrenaline produced inhibition of field stimulation-induced twitches. Its potency was similar in both operated and unoperated preparations, and nisoxetine (0.1 mumol/l) potentiated its effects to a similar extent (approximately 70-fold) in control and operated tissues. Responses to KCl in this half of the vas deferens were essentially unaffected by vasectomy. 7 Taken together, these findings indicate that post-ganglionic denervation of the epididymal half of the rat vas deferens by medial transection (vasectomy) leads to a slowly developing and prolonged supersensitivity to noradrenaline which is primarily due to the loss of the neuronal uptake facility. Persistent adaptive changes in the effector cells are apparently minimal after this means of denervation.
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PMID:Prolonged supersensitivity to noradrenaline of smooth muscle of the epididymal half of the rat vas deferens denervated by vasectomy. 289 40

The effects of inhibition of neuronal uptake upon the potency of the alpha-adrenoceptor antagonist phentolamine and upon the potencies of several agonists which produce inhibition of twitches evoked by field stimulation of the prostatic third of the rat vas deferens are described. In doses producing similar inhibition of the uptake of 3H-noradrenaline, cocaine produced a greater inhibition of the effects of (-)-noradrenaline than did desipramine or diphenhydramine. Cocaine differentially potentiated the effects of the sympathomimetic amines used such that the relative order of agonist potency was changed from xylazine greater than (-)-adrenaline greater than (+)-noradrenaline greater than (-)-metaraminol greater than or equal to (-)-noradrenaline greater than or equal to dopamine, to xylazine greater than (-)-adrenaline greater than (-)-noradrenaline greater than (-)-metaraminol greater than dopamine greater than or equal to (+)-noradrenaline. Prazosin enhanced and yohimbine reduced the twitch inhibition produced by (-)-noradrenaline in the absence of uptake blockers. In contrast, phentolamine had little effect upon the position of the log concentration curve for (-)-noradrenaline except when uptake was inhibited. These experiments demonstrate the marked influence of neuronal uptake upon estimates of the relative potencies of agonists activating alpha 2-adrenoceptors, and upon the estimate of the potency of phentolamine as an antagonist of noradrenaline at these receptors in this densely innervated tissue.
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PMID:The influence of neuronal uptake upon the relative potencies of agonists acting at prejunctional alpha 2-adrenoceptors in the rat isolated vas deferens. 612 31

Although hypertension is a well-established coronary risk factor, controlled, randomized hypertension drug trials have failed to show a definite preventive effect on the incidence of coronary heart disease. Possible adverse metabolic effects, particularly on blood lipids, of some commonly used antihypertensive drugs have been investigated. During the Oslo Study on the treatment of mild hypertension, which was not specifically designed to study the effect on lipids, a decrease in serum high-density lipoprotein cholesterol and an increase in serum triglycerides was observed with a combination of propranolol and hydrochlorothiazide. Therefore, special trials were designed specifically to study the effect of various antihypertensive drugs on blood lipids. Propranolol reduced serum high-density lipoprotein cholesterol (13 percent) and the cholesterol ratio [high-density lipoprotein cholesterol:(low-density lipoprotein cholesterol plus very low-density lipoprotein cholesterol)] by 15 percent and increased total serum triglycerides by 24 percent. Prazosin significantly (p less than 0.01) reduced total serum cholesterol, (9 percent) low-density lipoprotein cholesterol plus very low-density lipoprotein cholesterol (10 percent), and total triglycerides (16 percent), whereas the cholesterol ratio increased by 7 percent. The reduction in high-density lipoprotein cholesterol with propranolol plus prazosin was less than that with propranolol alone. Pindolol (with a high sympathomimetic activity) did not significantly change total cholesterol, low-density lipoprotein cholesterol plus very low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, or total triglycerides. Prazosin plus pindolol reduced serum low-density lipoprotein cholesterol plus very low-density lipoprotein cholesterol. The observed reductions in serum high-density lipoprotein cholesterol and the cholesterol ratio with oxprenolol were 11.5 percent and 13.7 percent, respectively, and with atenolol 16.7 percent and 19.2 percent, respectively, whereas total serum triglycerides were increased by 14.9 percent with oxprenolol and 17.9 percent with atenolol. Data provided by other European groups comparing the effect of antihypertensive treatment on lipid metabolism are also reviewed.
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PMID:Effect of alpha- and beta-blocker therapy on blood lipids: European experience. 614 44

The contractile response of canine tracheal muscle to i.a. phenylephrine, clonidine and norepinephrine was studied isometrically in situ in 32 dogs after beta adrenergic and ganglionic blockade. Intra-arterial phenylephrine caused dose-related tracheal contraction which was not altered by yohimbine (5 microgram/kg i.a.). Prazosin (4 mg/kg i.v.) caused a 77 +/- 3% decrease in tracheal response to i.a. phenylephrine. Clonidine also caused dose-related tracheal contraction, which was not altered by prazosin (4 mg/kg i.v.) but was 95 +/- 2% blocked by 5 microgram/kg i.a. of yohimbine. Norepinephrine caused tracheal muscle contraction which was greater than both phenylephrine (P less than .05) and yohimbine (P less than .001). Prazosin (4 mg/kg i.v.) caused 53 +/- 6% blockade and yohimbine (5 microgram/kg i.a.) caused 76 +/- 2% blockade of the response to i.a. norepinephrine; prazosin plus yohimbine caused greater than 98% blockade of the response to i.a. norepinephrine. The dose-response curve to i.a. acetylcholine was not altered by treatment with prazosin (4 mg/kg i.v.) plus yohimbine (5 microgram/kg i.a.). These results demonstrate that tracheal contraction induced by sympathomimetic amines is mediated by two subtypes of alpha adrenergic receptors on tracheal muscle, alpha-1 for phenylephrine, alpha-2 for clonidine and both alpha-1 and alpha-2 for norepinephrine.
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PMID:Evidence for two subtypes of alpha adrenergic receptors in canine airway smooth muscle. 626 89

Prazosin (Minipress; Pfizer), the first purely alpha-blocking antihypertensive agent, was used to treat 22 pregnant patients with moderately severe hypertension (diastolic blood pressure persistently above 95 mmHg at gestational ages ranging from 18 to 33 weeks). Prazosin was used because it is a postsynaptic alpha-blocking agent producing no direct tachycardia or renin stimulation and because its action in producing visceral vasodilation might improve uteroplacental perfusion. Oxprenolol (Trasicor; Ciba), a beta-blocking agent with intrinsic sympathomimetic activity, was added to the prazosin regimen in 12 cases. In this group pregnancy was prolonged for an average of 32 days and 10 infants survived the neonatal period. Fetal loss, mainly due to abortion, was high in the patients who had significant proteinuria, and it was not possible to prolong the pregnancy in these cases. There were no significant maternal, fetal or neonatal side-effects attributable to this combined alpha- and beta-blocking therapy, which may have both theoretical and practical advantages over other current therapies.
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PMID:Prazosin and oxprenolol therapy in pregnancy hypertension. 687 69

The effects of N,N'-bis-(O-methoxybenzylaminohexyl)-cystamine tetrahydrochloride (BHC), 2-brom-d-lysergic acid diethylamide (BOL) and prazosin on 5-hydroxytryptamine (5-HT) dose-response curves in rabbit ear artery and thoracic aorta were determined. BHC, an irreversible alpha-adrenoceptor antagonist, and prazosin had no substantial effect while BOL shifted the 5-HT dose-response curve to the right in aorta. BHC shifted the curve to the right and reduced maximal response to 5-HT in ear artery. BOL shifted the curve to the right only above 10(-6) M 5-HT in control, but at all concentrations studied in BHC-pretreated ear arteries. In vitro denervation of the ear artery with 6-hydroxydopamine did not significantly alter the 5-HT dose-response curve, nor the effect of BHC on that curve. On the other hand, desipramine decreased the contractile response to high concentrations of 5-HT in non-denervated ear arteries. Prazosin increased the 5-HT threshold and slope of the curve in the ED50 region, but had no inhibitory effect on contractile responses above 3 x 10(-7) M 5-HT or on maximal response. It is concluded that 5-HT acts exclusively on 5-HT receptors in aorta, but on both alpha-adrenergic and 5-HT receptors in ear artery. 5-HT also possesses a small indirect sympathomimetic action at high concentrations in the ear artery. Prazosin has no effect on 5-HT receptors in either vessel and blocks the alpha-adrenoceptor stimulation by 5-HT in ear artery.
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PMID:Receptors for 5-hydroxytryptamine in rabbit isolated ear artery and aorta. 747 Jun 33

Contractions, release of noradrenaline and release of ATP elicited by the indirectly acting sympathomimetic amine tyramine and responses elicited by exogenous noradrenaline were studied in the isolated vas deferens of the guinea pig. Release of noradrenaline was assessed as overflow of tritium after preincubation with [3H]-noradrenaline. ATP was measured by means of the luciferin-luciferase technique. In tissues pretreated with pargyline 1 mM, tyramine 300 microM, when added to the superfusion medium for 2 min, elicited contraction and an overflow of tritium (mainly [3H]-noradrenaline) and ATP. Contraction and ATP overflow responses were prevented and tritium overflow was greatly reduced by desipramine 10 microM. Prazosin 0.3 microM abolished contractions and evoked ATP overflow without changing tritium overflow. Blockade of postjunctional P2-purinoceptors by suramin 300 microM caused a marked decrease of tyramine-evoked contractions and a slight reduction of tritium overflow whereas evoked ATP overflow was markedly increased. The effect on contraction was not shared by two other P2-purinoceptor antagonists, namely pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) 32 microM and diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) 32 microM: PPADS increased contractions about fourfold, whilst DIDS had no effect at all. When the vas deferens was superfused for 24 min with medium containing tyramine 300 microM, evoked contractions and tritium overflow continued throughout whereas ATP overflow faded rapidly to basal values. In the presence of prazosin 0.3 microM, tyramine 300 microM again failed to elicit contractions as well as an overflow of ATP. Application of noradrenaline 10 microM instead of tyramine also resulted in prolonged contraction and an overflow of ATP that declined rapidly. It is concluded that all ATP released by tyramine is non-neuronal in origin, secondary to the activation of postjunctional alpha 1-adrenoceptors by released noradrenaline. The non-neural ATP does not seem to play a functional role in smooth muscle contraction and derives from a postjunctional source which is subject to a rapid depletion upon sustained alpha 1-adrenoceptor activation.
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PMID:Failure of tyramine to release neuronal ATP as a cotransmitter of noradrenaline in the guinea-pig vas deferens. 871 58

The herb Scoparia dulcis L. is used in Brazilian folk medicine to treat bronchitis, gastric disorders, haemorrhoids, insect bites and skin wounds, and in oriental medicine to treat hypertension. A previous study has shown that extracts of S. dulcis have analgesic and anti-inflammatory properties; in this work the sympathomimetic activity of an ethanolic extract of Scoparia dulcis L. has been investigated in rodent preparations in-vivo and in-vitro. Administration of the extract (0.5-2 mg kg-1, i.v.) to anaesthetized rats produced dose-related hypertension blocked by the alpha-adrenoceptor antagonist prazosin (1 mg kg-1). Partition of the extract in chloroform-water yielded an aqueous phase 20 times more potent than the extract; this produced hypertension in either reserpine-treated or pithed rats. In untreated and reserpine-treated rats the same fraction (1-3 x 10(3) micrograms mL-1) produced concentration-dependent contractions of the vas deferens musculature parallel to those obtained with noradrenaline (10(-8)-10(-4)M). Prazosin (10(-7)M) reduced the maximum contractile effect of the aqueous fraction, and shifted the concentration-response curves for noradrenaline to the right. The aqueous fraction (25 and 50 micrograms mL-1) increased the inotropism of electrically driven left atria of rats, the effect being blocked by propranolol (0.4 microgram mL-1). In preparations of guinea-pig tracheal rings the aqueous fraction (1-3 x 10(3) micrograms mL-1) relaxed the muscle contraction induced by histamine (10(-4) M) in proportion to the concentration. The effect was antagonized competitively by propranolol (1.5 microM). High-performance liquid-chromatographic analysis of the aqueous fraction revealed the presence of both noradrenaline and adrenaline in the plant extract. The results indicated that both catecholamines may account for the hypertensive and inotropic effects obtained after parenteral administration of S. dulcis extracts. This sympathomimetic activity is, however, unrelated to the previously reported analgesic and anti-inflammatory properties of the plant extract, but may explain its effectiveness upon topical application in the healing of mucosal and skin wounds.
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PMID:Sympathomimetic effects of Scoparia dulcis L. and catecholamines isolated from plant extracts. 883 98

The hypophagic action of the sympathomimetic amine ephedrine (EPH) in the rat may reflect actions on central dopaminergic (DA) and noradrenergic (NE) systems. EPH indirectly facilitates DA and NE activity and acts as a partial agonist at alpha(1)-adrenergic receptors. Two approaches were used to assess the possible contribution of NE and DA pathways to EPH-induced hypophagia. In the first, regression analyses of published archival data were computed to characterize the relation between the hypophagic potency values of (-)-(EPH) and related sympathomimetic drugs, including (+)-amphetamine, aminorex, mazindol, and phentermine (data derived from Blosser JC et al., 1987) and the most potent action of these drugs on facilitating NE activity or DA activity in rat brain (data derived from Rothman RB et al., 2001). In the NE analyses, the ED(50) values for these drugs for the inhibition of eating in rats were significantly related (r = 0.91, P = 0.03) to the potency of each drug in facilitating NE activity (either release or inhibition of [(3)H]NE reuptake), whereas in the DA analyses the correlation between ED(50) values and DA activity for these drugs was also significant (r = 0.98, P = 0.003). The regression analyses are thus supportive of a role for NE or DA in the hypophagic capacity of EPH. Although an earlier study noted that administration of the putative DA antagonist pimozide in rats attenuated EPH hypophagia, pimozide exerts similar potency in antagonizing DA receptors and alpha(1)-adrenergic receptors. To clarify the role of alpha(1)-adrenoceptors in EPH-induced hypophagia, adult male rats were pretreated with the alpha(1)-adrenergic receptor antagonist prazosin (0.0.5 and 2 mg/kg) prior to the administration of (-)-EPH (0, 5, 10, or 20 mg/kg, IP). Prazosin pretreatment at 2.0 mg/kg significantly attenuated the hypophagia, but not the hypodipsia, induced by administration of 10 mg/kg and by 20 mg/kg (-)-EPH. Collectively, these results confirm a critical contribution of of alpha(1)-adrenoceptors to the hypophagic action of (-)-EPH in rats.
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PMID:Noradrenergic modulation of ephedrine-induced hypophagia. 1255 68

Ophthalmologic surgical interventions are performed in numerous cases under general anaesthesia with halothane, many of which requiring a preoperatory mydriasis. Neosinerfin is alpha-adrenoceptive sympathomimetic. Local use, in a 10% concentration produces a strong mydriasis, resistant to the opening of the aqueous chamber during the intervention. Its systemic effects are remarkable: it induces a peripheral blood vessel constriction which can unleash a reflex bradycardia followed by a shortcoming of the cardiac flow. The halothane has various effects upon the heart: reduces the cardiac frequency, reduces the conduction speed of the cardiac impulse stimulating rhythm disorders, sensitizes the myocardium to the action of adrenaline, diminishes the heart's contraction force and the cardiac flow. The cumulative effects of seosinefrin and halothane cause major cardio-vascular changes: sinus bradycardia, ventricular arrhythmia, arterial hypotension. These are reasons for which the pre- and intraoperatory use of neosinefrin is unadvisable. Under this circumstances the collaboration between the ophthalmologist and anesthesiologist is very important, each of them having specific tasks. The ophthalmologist: preoperatory, the optimal pupillary dilatation may be obtained with tropicamide and diclofenac 0.1%, preoperatory, if the general anesthesia must be combined with local anesthesia, anesthetics in association with adrenalin should not be used; immediately postoperatory local use of atropine should be applied with cautiousness. The anesthesiologist: preoperatory he will not interrupt anti-hypertensive, anti-arrhythmia, anti-angina medication, with the mention that adrenoceptive alpha blockers (Prazosin) are indicated in comparison to adrenoceptive beta blockers because they diminish the risk of rhythm disorders; the use of clonidine and avoiding of phenobarbital in the premedication of the patient. As far as it is possible, it is recommended that halothane is replaced with izofluran or enfluran or enfluran which have a great tolerance to exogenous adrenoceptives.
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PMID:[Neosynephrine mydriasis combined with general anesthesia with halothane in ocular surgery]. 1267 10


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