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

The hypotensive mechanisms of pindolol in anesthetized and conscious rats were investigated. Pindolol caused a fall in blood pressure in anesthetized, conscious and spinal rats, though in conscious rats a higher dose of the drug was required to produce such a response. This hypotension with pindolol in anesthetized and conscious rats was markedly inhibited by pretreatment with the drug itself or other beta-adrenoceptor blocking drugs. A similar phenomenon also occurred when isoproterenol was injected intravenously in anesthetized and conscious rats. The relationship between the hypotensive actions of four beta-adrenoceptor blocking drugs in anesthetized rats and their intrinsic beta-sympathomimetic actions in isolated catecholamine-depleted tracheal preparations was determined. Order of hypotensive potencies was the same as that of their intrinsic beta-sympathomimetic action, namely, pindolol greater than carteolol greater than bufetolol in equilibrium propranolol (p less than 0.05). These results suggest that the hypotension with pindolol is mediated through a decrease in the peripheral vascular resistance due to an intrinsic beta-sympathomimetic action of the drug.
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PMID:Analysis of hypotensive mechanisms of pindolol, a beta-adrenoceptor blocking drugs in rats. 1 31

A double-blind comparison of 2 and 3 mg oral doses of carbuterol, a beta sympathomimetic drug with preferential selectivity for bronchial smooth muscle, was made with 25 and 35 mg doses of ephedrine sulfate over a six-month period in 26 patients with bronchial asthma. Spirometry was done before and three hours after administration of 3 mg of carbuterol or 35 mg of ephedrine sulfate at intervals of two weeks and one, four and six months. The data suggest a cumulative improvement in pulmonary function status with continued oral carbuterol use over the six-month period. However, the clinical effectiveness of the drug on pulmonary function was not clearly distinguishable from that of ephedrine in the present study.
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PMID:Double-blind trial of oral carbuterol in bronchial asthma. 1 57

This study reports on effects of beta-sympathomimetic drugs on the exocrine function of the isolated cat pancreas. The injection of these drugs resulted in an increase of pancreatic protein and enzyme secretion, the excretion of calcium into the juice and the rate of volume output were not changed. The enzyme secretion was inhibited by different adrenolytic drugs (phenoxybenzamine, practolol, butoxamine), by tetracain, hemicholinium, and atropine. The pancreatic function of cats pretreated by reserpine or 6-hydroxydopamine was not altered. It is concluded, that beta-sympathomimetic drugs influence the pancreatic protein and enzyme secretion in a cholinergic way. These results are consistent with those of other investigators showing a suppressibility of the isoproterenol-induced pancreatic amylase secretion by atropine.
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PMID:[The effect of sympathomimetric drugs on exocrine pancreatic function. Studies in the isolated cat pancreas (author's transl)]. 2 Jun 53

The positive inotropic and chronotropic responses of guinea-pig isolated left and right atria to 17 sympathomimetic amines were examined under conditions selected to control the pharmacological environment. Each agonist was compared with (--)-isoprenaline as the reference by constructing dose-response curves. Equiactive molar concentration ratios relative to (--)-isoprenaline were calculated at the EC50 for rate and tension responses. Statistical analysis revealed that (--)-noradrenaline and (+/-)-alpha-methylnoradrenaline were tension selective whereas (+/-)-alpha-ethylisoprenaline and N-methyldopamine were rate selective relative to (--)-isoprenaline. However, no structural trends emerged. The rank order of potency varied slightly between rate and tension, but an analysis of the regression and correlation coefficients indicated respectively that the equiactive molar concentration ratios and the rank orders could be considered identical on rate and tension. Antagonism of the (--)-isoprenaline-induced rate and tension responses by acebutolol, atenolol, practolol and propranolol was assessed from the pA2 values which were almost identical for both parameters with each antagnosti. It is concluded that the beta1-adrenoceptors mediating the positive inotropic and chronotropic responses do not warrant subdivision into two separate groups.
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PMID:Evidence from agonist and antagonist studies to suggest that the beta1-adrenoceptors subserving the positive inotropic and chronotropic responses of the heart do not belong to two separate subgroups. 2 Dec 38

Subtetanic contractions of the guinea-pig isolated soleus, a slow-contracting skeletal muscle, were evoked by transmural field-stimulation. Isoprenaline caused a dose-dependent depression of the contractions. This effect was inhibited by propranolol and H 35/25 (1-(p-tolyl-2-isopropylamino-1-propanol) but not by practolol. Similar results were obtained for terbutaline. Tazolol and H 80/62 (1-isopropylamino-3-(p-hydroxyphenoxy)-2-propanol (HCl), selective beta1-agonists, had no effect per se but inhibited the effect of terbutaline. Adrenaline, noradrenaline, and dopamine all caused a dose-dependent decrease in the force of the soleus contractions, their potencies being in that order. Tyramine did not appreciably affect the contractions nor did it inhibit the effect of terbutaline. Pretreatment with reserpine, if anything, increased the response to terbutaline. It is concluded, in conformity with previous in vivo studies, that the adrenergic receptor mediating the effect on the soleus muscle contractions is of the beta2-type. Indirect sympathomimetic effects do not contribute to the responses observed on the isolated soleus muscle.
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PMID:Analysis of the beta-receptor mediated effect on slow-contracting skeletal muscle in vitro. 2 Dec 60

Using timed collection of blood returning via the renal veins, the renal blood flow was determined in anaesthetized dogs, following the intravenous injection of 3 beta-adrenergic blockers, namely propranolol, oxprenolol and pindolol. The test drugs were given as a bolus or as an infusion, and their effects on the renal blood flow and blood pressure were studied. All the test drugs produced diminution in both the renal blood flow and blood pressure. However, these effects were variable in degree. The diminution in the renal blood flow under the influence of beta-adrenergic blockers might be explained by concomitant reduction in the cardiac output and/or blockade of the renal vasodilator beta-adrenergic receptors. An added factor might by sympathetic stimulation with consequent renal vasoconstriction in the case of blockers with intrinsic sympathomimetic activity. Beta-adrenergic blocking drugs should be given with extreme caution in cases with impaired renal function.
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PMID:Effect of some beta-adrenergic blocking drugs on the renal bloow flow in dogs. 2 82

The beta-blocking agent 1-(4-acetoxy-2,3,5-trimethylphenyloxy)-3-isopropylamino-propan-2-ol (metipranolol) was compared with propranolol and pindolol. The beta-blocking activity on isoproterenol induced tachycardia was determined in rabbits (ED250bpm). The following doses in microgram/kg i.v. were required to produce the same inhibition: 410 propranolol; 160 metipranolol; 130 pindolol. When intrinsic sympathomimetic activity was determined in reserpinized rats metipranolol was found to produce less than 10% of the increase in heart rate induced by a standard isoproterenol dose (1 mg/kg i.p.), whereas propranolol caused less than 20% and pindolol ca. 60%. The membrane stabilising activity, determined by the elevation of the fibrillation threshold (ED delta100muA) in rabbit hearts, was found to be greatest with propranolol (0.98 mg/kg i.v.) and least with metipranolol (1.68 mg/kg), with pindolol occupying an intermediate position (1.10 mg/kg). The cardioprotective action to hypoxia stress of metipranolol in rats was found to be the best, requiring a dose of only 5 microgram/kg i.p. compared with values of 28 microgram/kg for pindolol and 250 microgram/kg for propranolol. These results show that metipranolol has a high beta-sympatholytic activity which is not accompanied by either marked intrinsic activity or membrane-stabilising properties. The relatively marked cardioprotective action, which is probably due to a metabolic action, is particularly noteworthy.
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PMID:Experiments in animals on the pharmacological effects of metipranolol in comparison with propranolol and pindolol. 2 98

1 When cat spleen slices were exposed to a potassium-enriched (140 mM) Krebs solution, 367 +/- 31 ng g-1 5 min-1 of noradrenaline (NA) was released into the bathing medium. 2 Phenylephrine and clonidine (10(-7) to 10(-3) M) did not significantly modify the potassium-evoked NA release; acetylcholine decreased it in a dose-dependent manner. 3 Phenoxybenzamine increased NA release by 50% but phentolamine did not alter it; high concentrations of this drug greatly decreased NA release. Cocaine increased the NA release by about 30%. 4 It is suggested that the failure of sympathomimetic amines to depress, and of alpha-adrenoceptor blocking agents to enhance the release of NA by high potassium concentrations may be related to prolonged depolarization of the nerve terminals, which may desensitize presynaptic alpha-receptors. The fact that the same drugs are able to modify NA release during electrical nerve stimulation may be ascribed to the much shorter periods of depolarization occurring under these conditions.
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PMID:Release of noradrenaline from cat spleen slices by potassium. 2 81

Marked hyperglycaemia and hyperinsulinaemia were observed in two normal women in premature labour treated with an intravenous infusion of a beta-sympathomimetic drug and intramuscular dexamethasone injections. Similar therapy in a chemical diabetic patient caused diabetic ketoacidosis, while treatment of an insulin dependent diabetic with dexamethasone alone resulted in a major increase in her insulin requirements. It is suggested that the diabetogenic effects of beta-sympathomimetic drugs and dexamethasone may be additive and that regular plasma glucose estimations should be made when they are used, especially in patients with impaired glucose tolerance.
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PMID:Metabolic effects of beta-sympathomimetic drugs and dexamethasone in normal and diabetic pregnancy. 2 59

The effects of the classical alpha-sympathomimetic drugs naphazoline, tramazoline, xylometazoline, tetryzoline and oxymetazoline on blood pressure and heart rate of pentobarbitone-anaesthetized (75 mg/kg; i.p.) normotensive rats were studied following intravenous injections. With the aid of this experimental animal model a dose dependent decrease in mean arterial pressure and heart rate could be established for these agents, oxymetazoline excepted, for which only the bradycardia could be quantified. It is suggested that central alpha-adrenoceptors are involved in the mechanism of this cardiovascular inhibition in view of the most specific alpha-adrenoceptor-stimulating properties of these ddrugs. Additionally, the results indicate that the use of pentobarbitone as the anaesthetic enhances the hypotensive action of these agents, so that their pronounced peripheral vasopressive response can be overcome.
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PMID:Hypotensive and bradycardic effects of classical alpha-sympathomimetic drugs upon intravenous administration to pentobarbitone-anaesthetized rats. 2 53


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