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At least 433 records · Page 24Linked to original sources
PubMed1989

Strain-specific effects of antidepressants on escape deficits induced by inescapable shock.

The effects of several antidepressants (desmethylimipramine, amitriptyline and bupropion) on escape deficits induced by inescapable shock were assessed in four strains of mice. The extent of the escape interference engendered by inescapable shock varied across strains of mice. These deficits of escape performance were differentially affected by the drug treatments across strains. Repeated administration of desmethylimipramine eliminated the escape interference in A/J, but did not affect the performance in Balb/cByJ, C57BL/6J or CD-1 mice. Bupropion, in contrast, had a modest effect only in CD-1 mice. Unlike these compounds, the 5-HT reuptake blocker, amitriptyline, was found to influence escape performance irrespective of whether the drug was acutely or chronically applied. It is suggested that (a) the relative contributions of various mechanisms subserving the escape interference may vary across strains of mice, hence accounting for the strain-specific effects of the drug treatments, and (b) various antidepressants influence performance by affecting different components of the behavioral output, some of which may be apparent after acute treatment while others are expressed only after repeated treatment with the compound.

Amitriptyline↗
PubMed1981

Pharmacokinetics of bupropion, a novel antidepressant agent, following oral administration to healthy subjects.

The pharmacokinetics of bupropion hydrochloride, a structurally novel antidepressant agent, have been studied in healthy male and female subjects following administration of single oral doses of 50, 100 and 200 mg. Plasma drug concentrations were determined directly by a specific radioimmunoassay (r.i.a.), while urinary measurements required a prior solvent extraction to remove substances interfering in the assay. Bupropion appeared rapidly in the plasma, suggesting good absorption. Drug plasma concentration-time data were fitted well to a two-compartment open model of drug disposition by use of the computer program NONLIN. By comparison of AUC, Cmax and tmax values, the pharmacokinetics of bupropion were found to be linear across the 50-200 mg dose range in both sexes. When the data were normalized for subjects' body weights, no differences between pharmacokinetic parameters for male and female subjects were found. Mean disposition half-lives across treatments were 1.2-1.4 h for t1/2 alpha and 10.7-13.8 h for the t1/2 beta. Bupropion was extensively bound (85%) to human plasma proteins over a wide drug concentration range. Less than 1% of a 200 mg oral dose of bupropion hydrochloride appeared in the urine of 16 subjects as unchanged drug, indicating extensive metabolism of the parent compound.

Administration, Oral↗
PubMed1985

The saturability of a site of loss and the degree of supersensitivity to agonists which are substrates of this site of loss.

The present investigation was undertaken to test the hypothesis that the experimentally determined degree of supersensitivity to an agonist caused by inhibition of a site of loss depends on the ratio "Km of the site of loss/ED50 of the agonist". The influence of inhibition of neuronal uptake by cocaine on the alpha-adrenoceptor-mediated effect of noradrenaline was studied on the dog saphenous vein; the influence of inhibition of COMT by U-0521 on the beta-adrenoceptor-mediated effect of isoprenaline was studied on the dog saphenous vein and on the guinea-pig trachea; the influence of inhibition of acetylcholinesterase by physostigmine on the effect of acetylcholine was studied on the guinea-pig ileum. To further extend the range of values of the ratio "Km/ED50", several concentrations of phentolamine, propranolol or atropine were used to "increase the ED50" of the respective agonist. It was thus possible to determine the degree of supersensitivity caused by inhibition of a site of loss over a range of "Km/ED50" values of 0.02 to 2,307. In seven situations the ratio "Km/ED50" was higher than 10. In all of these cases the supersensitivity caused by inhibition of the site of loss was maximal. In eleven situations the ratio "Km/ED50" was less than 10 and higher than 0.1 and the supersensitivity obtained was sub-maximal but was closer to the maximum, the closer the ratio was to 10. In two situations the ratio was less than 0.1 and no supersensitivity was obtained. The results confirm the hypothesis.

Acetylcholine↗
PubMed1983

Cardiovascular actions of kynuramine and 5-hydroxykynuramine in pithed rats.

Kynuramines occur endogenously in brain and peripheral tissues as metabolites of indoleamino acids and indolamines but little is known regarding their possible physiological and/or pharmacological activity. The present study has investigated the effects of kynuramine and 5-hydroxykynuramine on the cardiovascular system of pithed rats and attempted to correlate effects seen on adrenergic and serotonergic receptors with ligand binding experiments done in vitro using rat brain membranes. Kynuramine was found to release cardiac catecholamines and to act as a weak partial agonist on vascular alpha-adrenoceptors. Hydroxylation in the 5-position (5-hydroxykynuramine) did not alter cardiac potency but increased pressor activity 100-fold. Vasopressor responses to 5-hydroxykynuramine were mediated via a dual agonistic action on both postsynaptic alpha 2-adrenoceptors and vascular serotonin2 receptors. These findings were supported by ligand binding studies, in which both kynuramine and 5-hydroxykynuramine showed affinity for cortical [3H]spiroperidol and [3H]clonidine binding sites. Overall, the results show that kynuramines can exert peripheral (and possibly central) actions which may prove to be of physiological and/or pharmacological significance.

Adrenergic alpha-Agonists↗
PubMed1987

Potentiation of central effects of L-dopa by an inhibitor of catechol-O-methyltransferase.

The effects of a COMT-inhibitor, U-0521, and a MAO-B-inhibitor, 1-deprenyl, on L-dopa-induced circling behaviour were compared in 6-OHDA-lesioned rats. The actions of U-0521 and 1-deprenyl on the anti-cataleptic effect of L-dopa were also studied. Both U-0521 and 1-deprenyl were found to potentiate L-dopa-induced circling behaviour and anti-cataleptic effect of L-dopa. In both test systems the L-dopa potentiation of 1-deprenyl was longer-lasting than that caused by U-0521. Thus inhibition of COMT, like inhibition of MAO, is able to enhance the central effects of L-dopa. This principle might be beneficial in the treatment of Parkinson's disease especially if COMT-inhibitors with greater performance can be developed.

Animals↗
PubMed1980

[Electrophysiological classification of newer antiarrhythmic drugs (author's transl)].

Newer antiarrhythmic drugs are tentatively classified on the basis of their influence on the transmembrane action potential, the fast sodium inward current and its kinetics, and the slow inward current which is primarily carried by calcium ions. Disopyramide is probably a quinidine-like antiarrhythmic drug, while the effects of aprindine, lorcainide, and tocainide resemble those of lidocaine. Mexiletine and propafenon cannot be classified definitely on the basis of the hitherto available electrophysiological data. Besides their effects on the fast inward current these substances may have additional calcium antagonistic properties.

Action Potentials↗
PubMedDate not supplied

Influence of drugs on the relationship between sinus node recovery time and calculated sinoatrial conduction time in man.

Sinus node recovery time (SRT), the pacing rate with the maximal SRT, and calculated sinoatrial conduction time (SACT) were studied by overdrive atrial pacing and programmed premature atrial stimulation in 78 patients before and after the application of several antiarrhythmic drugs or of atropine. The maximum SRT was usually observed at lower rates of atrial pacing after application of a drug that prolonged SACT, whereas the opposite behaviour was observed in the majority of cases in whom the drug tested shortened calculated SACT. However, this relationship was not observed in all cases which may be due to random changes of sinus node automaticity or sinoatrial conduction, or to the inability of programmed premature atrial stimulation to detect changes of SACT. The results of this study further substantiate the importance of the properties of sinoat;ial conduction for achieving a maximal depression sinus node activity during high rate atrial pacing.

Anti-Arrhythmia Agents↗