ABSTRACT
Effect of B-HT 920, a selective alpha 2 adrenoceptor agonist, was studied on ouabain induced cardiac arrhythmias and cardiac arrest in guinea pigs. Ventricular premature beats, ventricular tachyarrhythmias and cardiac arrest were induced in anaesthetized guinea pigs by slow infusion of ouabain. B-HT 920 accorded significant protection to guinea pigs against ouabain induced arrhythmias. Yohimbine inhibited the antiarrhythmic effect of B-HT 920 significantly. It is concluded that the protective effect of B-HT 920 against ouabain induced cardiac arrhythmias and cardiac arrest is mediated through the stimulation of alpha 2 adrenoceptors.
Subject(s)
Adrenergic alpha-Agonists/pharmacology , Animals , Arrhythmias, Cardiac/chemically induced , Azepines/pharmacology , Female , Guinea Pigs , Heart/drug effects , Heart Arrest/chemically induced , Male , Ouabain/toxicityABSTRACT
Cardiac arrhythmias and cardiac arrest were induced in pentobarbitone anaesthetised cats by slow intravenous infusion of ouabain. The dose of ouabain required for the induction of the stages of arrhythmias and cardiac arrest and the maximum pressor effect induced by ouabain were assessed in control and clonidine pretreated cats. Clonidine caused significant delay in the onset of cardiotonic effects of ouabain and inhibition of the maximum pressor effect of ouabain. The inhibition of cardiotoxic and pressor effects of ouabain may be the result of clonidine's effect on the neural components of ouabain action.
Subject(s)
Animals , Arrhythmias, Cardiac/chemically induced , Blood Pressure/drug effects , Cats , Clonidine/pharmacology , Female , Heart Arrest/chemically induced , Heart Diseases/chemically induced , Hemodynamics/drug effects , Male , Ouabain/antagonists & inhibitorsSubject(s)
Acetylcholine/pharmacology , Animals , Blood Pressure/drug effects , Cardiovascular System/drug effects , Cats , Dimethyl Sulfoxide/pharmacology , Dose-Response Relationship, Drug , Drug Interactions , Female , Guinea Pigs , Heart Rate/drug effects , Ileum/drug effects , Male , Mice , Motor Activity/drug effects , Muscle Contraction/drug effects , Rats , Serotonin/pharmacology , Solvents/pharmacology , Uterus/drug effectsABSTRACT
Dimethylformamide (DMF) is widely used as a drug solvent. We found DMF to have wide-spread pharmacological effects including depressant effect on CNS evidenced by a decrease in locomotor activity, body and limb tone and rectal temperature, and potentiation of pentobarbitone sleep. A dose-dependent hypotensive effect was seen in cats and rats. In rats, it was partially blocked by atropine and was associated with bradycardia. DMF antagonised the contractions of smooth muscle induced by many agonists. An atropine sensitive spasmogenic effect was observed on rabbit ileum at 20 ml/l and a direct relaxant effect at 50 ml/l. A positive inotropic effect on guinea pig atria was observed with 5 ml/l. The results indicate DMF concentrations that may not perhaps produce 'solvent artifacts' when used as a solvent.