ABSTRACT
The intravenous infusion of oxytocin in urethane anaesthetized rabbits induced marked increases of both atrial and ventricular fibrillation threshold. The heart rate and the arterial blood pressure (BP) diminished. Since there was no parallelism between the fibrillation threshold changes and those of heart rate and BP, it might be concluded that the changes of the fibrillation thresholds were very likely primary, i.e. they were due to the modifications of the electrophysiological properties of the heart. The intravenous infusion of 0.5% chlorbutol , a preservant widely used in many commercial preparations induced only minor changes of the investigated parameters.
Subject(s)
Atrial Fibrillation/physiopathology , Oxytocin/pharmacology , Ventricular Fibrillation/physiopathology , Animals , Blood Pressure/drug effects , Chlorobutanol/pharmacology , Female , Heart Rate/drug effects , Infusions, Parenteral , Male , Oxytocin/administration & dosage , RabbitsABSTRACT
A study on the atrial and ventricular fibrillation thresholds performed in urethane anaesthetized rabbits showed that no significant change occurred until blood pressure was reduced to 40% of the initial value. Bilateral cervical vagotomy and the administration of propantheline did not affect these changes. (DL) propranolol (0.2 mg/kg i.v.) "unmasked" a tendency of CaCl2 to elevate the fibrillation threshold; it also increased the lethal calcium level.
Subject(s)
Atrial Fibrillation/chemically induced , Calcium Chloride/administration & dosage , Ventricular Fibrillation/chemically induced , Animals , Blood Pressure/drug effects , Calcium/blood , Female , Heart Rate/drug effects , Hemorrhage/physiopathology , Infusions, Parenteral , Male , Maximum Allowable Concentration , Propranolol/pharmacology , Rabbits , VagotomySubject(s)
Arrhythmias, Cardiac/etiology , Calcium/pharmacology , Animals , Arrhythmias, Cardiac/chemically induced , Dogs , Female , MaleSubject(s)
Anti-Inflammatory Agents , Dihydrotestosterone/pharmacology , Nitrates/pharmacology , Testosterone/analogs & derivatives , Testosterone/pharmacology , Animals , Cardiovascular System/drug effects , Coronary Vessels/drug effects , Dogs , Female , Male , Pituitary-Adrenal System/drug effects , Rats , Thyroid Gland/drug effects , Vasodilation/drug effectsABSTRACT
The intraarterial injections of 50% urea or 20% NaCl induced a rise of the systemic arterial blood pressure simultaneously with a constriction of the vessels of the legs. The mechanism which is responsible for these phenomena is very complex. It includes a reflex arising from the arterial wall, which is mediated through the spinal cord, the release of catecholamines and of some still nonidentified pressor substances and a central component which is normally masked by the depressor sinus reflex.
