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PubMed1977

Metabolic actions of some sympathomimetic amines and their acetyl derivatives in the rabbit.

To study how acetylation affects the activity of sympathomimetic amines the effects of tyramine, amphetamine, ephedrine, phenylephrine, orciprenaline and salbutamol and of their O- and N-acetyl derivatives on blood glucose and free fatty acid concentrations were studied in the rabbit. Hyperglycemia was induced by all parent compounds except amphetamine which tended to have a weak hypoglycaemic action. Hyperlipaemia in the doses used was induced by ephedrine and orciprenaline but not by the other parent compounds. Usually acetylation decreased the metabolic effects of the compounds but O-acetylation of tyramine and salbutamol caused hyperlipaemia and O-acetylation of ephedrine increased its fatty acid-mobilizing action, perhaps as a consequence of increased lipid solubility of the compounds. The ultimate effects of the O-acetyl derivatives were probably at least partly due to deacetylation at their sites of action. However O-acetylation of sympathomimetics could perhaps be used to induce drug latentiation.

Acetylation↗
PubMed1976

Characteristics of responses of isolated human fallopian tube to transmural stimulation and to sympathomimetic amines.

The responses of circular and longitudinal muscle of human fallopian tube to transmural stimulation and sympathomimetic amines have been investigated. It was found that tissues from the earlier part of the menstrual cycle (i.e., estrogen dominant) were less responsive to all stimuli than those from the middle or late phase of the cycle. Although excitatory alpha responses of ampulla and isthmus could be observed, the predominant response of ampulla and isthmus, in all phases of the menstrual cycle, to (--)-noradrenaline and transmural stimulation was inhibition of spontaneous activity. The inhibitory response to transmural stimulation, was abolished by tetrodotoxin and guanethidine. The inhibitory responses to transmural stimulation and (--)-noradrenaline were reversed by propranolol. These findings show that the response of tissues to transmural stimulation resulted from release of noradrenaline from adrenergic nerves, and subsequent action on inhibitory beta adrenergic receptors.

Electric Stimulation↗
PubMed1984

Mechanisms of cardiac supersensitivity to sympathomimetic amines.

Supersensitivity of the beta-adrenoceptor-mediated positive inotropic and chronotropic responses of the heart to sympathomimetic amines is considered. The various types of supersensitivity of both pre- and post-synaptic origins are described and the possible mechanisms involved are discussed. Emphasis is given to the supersensitivity that arises from depletion of sympathetic catecholamine stores by reserpine and 6-hydroxydopamine. Results are presented which indicate that in both cases the supersensitivity develops slowly, is specific for the beta-adrenoceptor and is not associated with an increase in affinity of agonists for the receptor. Radioligand binding data is presented to show that there is no increase in the total number of beta-adrenoceptor binding sites in membrane fractions from ventricular homogenates of animals receiving reserpine. A review of the literature on binding studies indicates two opposing views with respect to the effects of reserpine on beta-adrenoceptor binding sites, one showing no change and the other showing an increase in total binding sites. Limited studies in the literature show that 6-hydroxydopamine may increase the number of sites. Binding data therefore remains inconclusive and must be interpreted with caution. The relationship between the development of depletion-induced supersensitivity and the innervation of the tissue and its receptor type is discussed.

Animals↗
PubMed1968

Action of various sympathomimetic amines on the isolated stripped vas deferens of the guinea-pig.

1. The contractile potencies of some sympathomimetic amines and cholinergic drugs were studied in the isolated, stripped vas deferens of the guinea-pig.2. alpha-Methylnoradrenaline, adrenaline and metaraminol produced the same relative maximal responses as noradrenaline, which served as reference drug; on the other hand, octopamine, dopamine and alpha-methyldopamine were much less active. Short term pretreatment of the animals with reserpine did not affect the maximal relative responses.3. Tyramine, alpha-methyl-m-tyramine and hordenine methiodide had little effect on the untreated preparation. In the presence of just threshold concentrations of noradrenaline, the relative maximal responses to tyramine and hordenine methiodide were markedly increased.4. The relative maximal response to carbachol was the same as that to noradrenaline, while that to DMPP was smaller. In contrast to carbachol, the action of DMPP was potentiated by pretreatment of the preparation with noradrenaline.

Animals↗
PubMedDate not supplied

Colorimetric determination of sympathomimetic amines methyldopa and noradrenaline.

The chromogenic reagent p-dimethylaminocinnamaldehyde (PDAC) is introduced for the determination of the sympathomimetic amines methyldopa and noradrenaline. The method is based on measurement of the orange color developed when the alkaline solution of methyldopa and noradrenaline is allowed to react with PDAC at pH 5.0. The color developed obeys Beer's law in the concentration range 0.1-1.5 mL of 2 X 10(-3)M solution of noradrenaline and methyldopa. The results are compared with those obtained with another chromogenic reagent, p-dimethylaminobenzaldehyde (PDAB). Determinations on dosage forms of the drugs, using PDAC and PDAB reagents, agreed well with results of determinations by official pharmacopoeial methods.

Benzaldehydes↗
PubMed1973

Some actions of sympathomimetic amines and their antagonists on mouse superfused ileum.

Superfused segments of mouse ileum exhibited spontaneous movement which Mwere inhibited by sympathomimetic amines. Isoprenaline and adrenaline were approximately equipotent and about 15 times more potent than either noradrenaline or phenylephrine. Supersensitivity developed to all these agents when mice had been 'sympathectomized' with NGF-antiserum or 6-hydroxydopamine and it was more pronounced with the latter treatment. Responses to the amines were reduced by phentolamine and propranolol, alone or in combination, with the exception of phenylephrine, the responses to which were simply shortened in duration after,beta-adrenoceptor blockade. No qualitative changes were evident in the effects of the blocking agents after 'sympathectomy'.

Animals↗
PubMed1972

A structure-activity study of sympathomimetic amines on the beta-adrenoreceptors of guinea-pig trachea.

1. The relative activities of a large number of sympathomimetic amines were estimated on the beta-adrenoceptors of the guinea-pig tracheal chain preparation. Concentrations which produced half-maximal responses were measured for each drug and the maximum responses were also noted and expressed as a percentage of that produced by isoprenaline.2. The relative activities of the amines generally decrease with loss of hydroxyl groups from the structure, and amines with less than two hydroxyl groups produce little or no observable response.3. The affinity constants of the partial agonists and antagonists were measured. The hydroxyl group on the beta carbon atom of the side chain, N-alkyl groups and an alpha carbon methyl group increase affinity, whereas the p-phenolic group decreases affinity. The m-phenolic group does not seem to affect affinity.4. By comparing the effects of groups on affinity with their effects on activity, it was deduced that N-alkyl groups, m- and p-phenolic groups and probably also the beta carbon hydroxyl group increase efficacy. Alpha carbon methylation appears to reduce efficacy.

Amphetamine↗
PubMed1996

Influence of a sympathomimetic amine on masticatory and trapezius pain/pressure thresholds and electromyographic levels.

OBJECTIVES: This study examined the influence of terbutaline, a beta-adrenergic sympathomimetic amine on pain/pressure thresholds in the index fingers and masseter and trapezius muscles and electromyographic activity in trapezii. STUDY DESIGN: In a randomized and double-blind controlled trial, 20 asymptomatic female subjects were assigned to receive either an injection of terbutaline or sterile water before collection of pain/pressure thresholds and electromyographic levels. Repeated analysis of variance and paired t tests were calculated to test for baseline and postinjection differences between groups. RESULTS: No significant baseline or postinjection group differences in pain/pressure thresholds or electromyographic were detected. CONCLUSIONS: beta-adrenergic sympathomimetic stimulation does not influence pain/pressure thresholds or electromyographic activity in the masselet and trapezius muscles or pain/pressure thresholds in the index fingers. These results suggest that development of painful muscle conditions is not caused by elevations of sympathetic activity.

Adolescent↗
PubMed1962

Comparison of bretylium and guanethidine: tolerance, and effects on adrenergic nerve function and responses to sympathomimetic amines.

Bretylium depresses the slope of regression lines relating frequency of sympathetic nerve stimulation to magnitude of contractions of the cat nictitating membrane. In contrast, guanethidine and reserpine preferentially abolish responses to low rates of nerve stimulation and cause a roughly parallel shift of the regression lines. The hypersensitivity of the nictitating membranes of cats to intravenous adrenaline or noradrenaline is far greater after a series of small daily doses of bretylium or guanethidine than after single large doses. The maximal sensitivity produced was similar to that after postganglionic sympathetic nerve section and exceeded that produced by ganglion blockade. The development of hypersensitivity to catechol amines is accompanied by some return of responses of the nictitating membranes to sympathetic nerve stimulation despite continued daily administration of bretylium or guanethidine. In cats given bretylium daily, responses to low rates of nerve stimulation become greater than in controls unless the dose of bretylium given subcutaneously is 50 mg/kg or more. When marked hypersensitivity to catechol amines has been produced by giving bretylium or guanethidine daily for 7 or 14 days, the sympathomimetic effects of these compounds are greater. Responses to intravenous dimethylphenylpiperazinium are also increased and the results suggest that even large daily doses of adrenergic neurone blocking agents do not appreciably impair the functioning of the adrenal medulla. The pressor effects of intravenous adrenaline, noradrenaline and dimethylphenylpiperazinium iodide increase less than the corresponding nictitating membrane responses. These results are discussed in relation to tolerance to adrenergic neurone blockade, and differences between the effects of bretylium and guanethidine found in man. Bretylium and guanethidine depress the slopes of the dose-response curves for the pressor and nictitating membrane contracting effects of tyramine. When single doses or a short series of daily doses were given, guanethidine caused more depression of the slopes than did bretylium, but nevertheless large depressions of slope were found after giving bretylium daily for several weeks. The magnitude of the responses can be greater or less than in controls depending on the dose of the sympathomimetic amine, the dose of the adrenergic neurone blocking agent and the duration of its administration. The results suggest that injection of tyramine produces a progressively smaller release of adrenaline or noradrenaline during the daily administration of bretylium (or guanethidine) but that in some test situations this is more than compensated for by the development of hypersensitivity to the catechol amine released. Some corresponding changes in responses to amphetamine and ephedrine are also described.

Adrenergic Agents↗
PubMed1979

Failure of dibutyryl and 8-bromo-cyclic GMP to mimic the antagonistic action of carbachol on the positive inotropic effects of sympathomimetic amines in the canine isolated ventricular myocardium.

Effects of carbachol, dbcGMP and 8-bromo-cyclic GMP on the positive inotropic actions of sympathomimetic amines and dbcAMP were studied on the canine isolated right ventricular myocardium. Carbachol alone did not substantially change the developed tension of the muscle, but did markedly shift the dose response curve for isoprenaline on the developed tension to the right and depressed the maximal response to the drug in a concentration dependent manner. The positive inotropic action of phenylephrine was affected by carbachol in the same manner as that of isoprenaline. DbcGMP in concentrations of 10(-3) M and higher produced a significant increase in the developed tension. The positive inotropic action of dbcGMP was partly inhibited by a beta-adrenoceptor blocking agent, pindolol. In the presence of dbcGMP, isoprenaline produced an action similar to that seen in the control experiment, but this action was not maintained on such a steady state level as in the control. This rapid decline of the effect of isoprenaline in the presence of dbcGMP was prevented by adding ascorbic acid to the organ bath. The positive inotropic actions of phenylephrine and of dbcAMP were not substantially affected by dbcGMP. 8-Bromo-cyclic GMP in a concentration of 10(-4) M did not change either the basal developed tension or the positive inotropic actions of noradrenaline and of isoprenaline. The present results indicate that these cyclic GMP derivatives are not able to mimic the antagonistic action of cholinergic stimulation on the positive inotropic action of adrenergic stimulation on the positive inotropic action of adrenergic stimulation on the canine ventricular myocardium.

Animals↗
PubMed1962

Response of normal, denervated, and reserpine-treated arteries to sympathomimetic amines and nicotine in dogs.

The sensitivity of normal, denervated carotid arterial segments, and of carotid arteries of dogs previously treated with reserpine, to sympathomimetic amines and nicotine has been compared using isolated perfused segments of these vessels. Arteries from animals and arterial segments treated with reserpine, denervated by peri-arterial stripping or by re-anastomosing of segments removed and reversed, both showed an increased sensitivity to noradrenaline which correlated well with a decrease in tissue noradrenaline content. Tyramine did not produce vasoconstriction in denervated vessels, but some constriction was observed when the vessels had been pretreated with noradrenaline or with dopamine or dopa. The effect of nicotine upon dog carotid arterial segments was recorded 130 times. The most frequent response was vasodilatation. This involved both the arterial wall per se and the vasa vasorum. The vasodilatation in response to nicotine was seen in arteries from normal and reserpine-treated animals and in denervated vessels.

Animals↗
PubMed1959

A hypothesis concerning the effect of cocaine on the action of sympathomimetic amines.

There is a store, perhaps in chromaffin tissue, of noradrenaline in tissues with a sympathetic innervation. The store is depleted by treatment with reserpine. Sympathomimetic amines like tyramine act only when this store is present and have no effect when the store is depleted. They also fail to act in the presence of cocaine. Catecholamines like noradrenaline have a much greater action than usual when the store is depleted, and they have a much greater action in the presence of cocaine. It is suggested that cocaine has the effect of blocking release from the store, so that the action of tyramine is abolished and the spontaneous release from the store which is responsible for the normal (low) sensitivity to noradrenaline is stopped. Noradrenaline is taken up into the store in the heart and the vessel wall from the blood, and the disappearance of noradrenaline from the blood is in part due to this uptake and not entirely to destruction. Cocaine may prevent this uptake of noradrenaline by the tissue stores. Experiments on rabbit atria, on the vessels of the rabbit ear and on the heart-lung preparation are described which are consistent with this hypothesis.

Animals↗
PubMed1987

Some aspects of the enzymic inactivation of sympathomimetic amines.

This review seeks to discuss the possible importance of monoamine oxidase (MAO) and semicarbazide-sensitive amine oxidase (SSAO) in terminating the effects of released sympathetic transmitters and in the inactivation of endogenous or administered sympathomimetic amines with particular reference to some aspects of the cardiovascular system. Use of in vitro preparations of blood vessels and of other smooth muscles, such as vas deferens and anococcygeus, has thrown light on possible roles for these deaminating enzymes, even in the inactivation of noradrenaline, while the new reversible inhibitors of MAO-A show promise as antidepressants with a reduced risk of hypertensive crises following the ingestion of tyramine-containing food. However, the role of SSAO in the in inactivation of amines remains an enigma, even though much is now known of its biochemical nature. While the pharmacological responses to amine substrates can be potentiated by inhibition of SSAO, there is a suspicion that it is product rather than substrate that is more important.

Amine Oxidase (Copper-Containing)↗
PubMed1988

Actions of sympathomimetic amines on the Ca2+ transients and contractions of rabbit myocardium: reciprocal changes in myofibrillar responsiveness to Ca2+ mediated through alpha- and beta-adrenoceptors.

The effects of sympathomimetic amines on Ca2+ transients and isometric contractions were assessed in isolated rabbit papillary muscles in which multiple superficial cells had been microinjected with the calcium-sensitive bioluminescent protein aequorin. In the presence of beta-adrenoceptor blockade, the alpha-receptor agonist phenylephrine increased both the amplitude of the aequorin signals and the force of contraction in a concentration-dependent manner. However, the maximum increase in the aequorin signals was less than 10% of that produced by the beta-receptor agonist isoproterenol, while the maximum increase in force of contraction produced by alpha-stimulation was about 50% of that elicited via beta-adrenoceptors. For a given increase in the force of contraction, stimulation of alpha-adrenoceptors produced much less change in the amplitude of the aequorin signals than did elevation of the extracellular Ca2+ concentration; we interpret this to mean that the positive inotropic effect of alpha-adrenoceptor stimulation is in large part the result of an increase in myofibrillar sensitivity to Ca2+. Stimulation of alpha-adrenoceptors produced little change or a slight decrease in the duration of the aequorin signal and an increase in the duration of contraction, while stimulation of beta-adrenoceptors significantly decreased the time to peak and duration of both the aequorin signals and the contractions. For a given level of inotropic effect, high concentrations of isoproterenol often increased the aequorin signals more than did elevations of Ca2+, which is consistent with other evidence that the cyclic AMP-dependent phosphorylation of troponin I leads to a decrease in myofibrillar Ca2+ sensitivity. However, concentrations of isoproterenol that did not produce evidence of this sort of desensitization also abbreviated the contractions much more than they did the aequorin signals. This suggests that the traditionally accepted mechanisms--a decrease in the Ca2+ affinity of troponin C and an acceleration of Ca2+ uptake by the sarcoplasmic reticulum--may not be sufficient to account for the actions of beta-receptor stimulation on the time course of contraction. In the absence of blocking agents, the naturally occurring catecholamines norepinephrine, epinephrine, and dopamine appear to influence the function of the rabbit papillary muscle through both alpha- and beta-adrenoceptors. Dopamine has a relatively greater effect on alpha-adrenoceptors than the other catecholamines.

Animals↗
PubMed1991

[Specific detection of urinary sympathomimetic amines for control of anti-doping by gas chromatography-mass spectroscopy].

A specific, sensitive and reliable gas chromatography-mass spectrometry (GC-MS) technique for detection of sympathomimetic amines following urinary extraction is proposed. Amphetamine, phentermine, ephedrine, mephenorex, methylphenidate, benzphetamine, clobenzorex and internal standard (fenfluramine) are extracted from urines at pH 7.0 using elution by chloroform-isopropanol on C18 cartridges. Derivatization followed by GC-MS analysis allows identification of these drugs founded on relative retention times and mass spectra. The quantitation limit for derivatizable drugs was found to be 200 ng/ml and 500 ng/ml for underivatizable drugs.

Amphetamines↗
PubMed1979

Similar effects of a monoamine oxidase inhibitor and a sympathomimetic amine on memory formation.

Amnesia resulting from inhibition of cerebral protein synthesis by cycloheximide can be prevented by subcutaneous injection of the monoamine oxidase inhibitor pargyline (25 mg/kg) or the sympathomimetic amine metaraminol (3.0 mg/kg) administered up to 30 min following learning of a single trial passive avoidance task in day-old chickens. The injection has to be made during the life time of labile memory for the prevention of cycloheximide-induced amnesia. On the other hand, amnesia induced by the Na/K ATP'ase inhibitor ouabain can only be prevented if these two agents are administered up to 5 min after learning, i.e. during the life time of short-term memory. In addition, both agents produce a retrieval deficit 90 min after the injection, but only when memory is in long-term storage. These results are compared to those obtained with administration of norepinephrine, d-amphetamine and diphenylhydantoin.

Animals↗
PubMedDate not supplied

The identification of sympathomimetic amines by Raman spectroscopy.

This study was undertaken to explore the feasibility of using Raman spectroscopy as a means of identifying drugs in the forensic laboratory. Raman spectra of a group of sympathomimetic amines, in pure form and in pharmaceutical preparations, were obtained and compared; group similarities and individual differences were found, and satisfactory identifications could be made. Water solutions as well as solids were examined. The procedure is rapid, sensitive, simple, and non-destructive.

Indicators and Reagents↗