ABSTRACT
The study examined the effect of clonidine hydrochloride (10-9-10-5 Ð) on electrical activity of working cardiomyocytes in rat right atrium. Stimulation of α2-adrenergic receptor with clonidine changed electrical activity of the heart. All tested concentrations of the agonist lengthened the action potential and decreased the firing rate of cardiomyocytes in a dose-dependent manner. The maximum effects of clonidine were observed at concentration of 10-5 Ð.
Subject(s)
Action Potentials/drug effects , Adrenergic alpha-2 Receptor Agonists/pharmacology , Clonidine/pharmacology , Myocytes, Cardiac/drug effects , Receptors, Adrenergic, alpha-2/physiology , Action Potentials/physiology , Animals , Animals, Outbred Strains , Dose-Response Relationship, Drug , Heart/drug effects , Heart/physiology , Heart Atria/cytology , Heart Atria/drug effects , Myocytes, Cardiac/cytology , Myocytes, Cardiac/physiology , Rats , Tissue Culture TechniquesABSTRACT
The study examined the effects of hyperpolarization-activated funny current (If) on HR and coronary flow in Langendorff-isolated hearts from newborn rats. Blockade of If current with ZD7288 changed the examined cardiac parameters. The blocker in a concentration of 10-9 M decreased HR by 26.8% (p≤0.05). In concentrations 10-8, 10-7, 10-6, and 10-5 M ZD7288 produced minor differently directed effects. In a concentration of 10-5 M, ZD7288 reduced coronary flow in the isolated heart (p≤0.01). In other concentrations, the blocker produced no significant effects on coronary flow.