Emmanuel B. Thompson

Time course of epinephrine-induced arrhythmias in cats exposed to dichlorodifluoromethane.

Abstract Inhalation of high concentrations of aerosol propellants, e.g., CCl2F2, is known to cause sudden death in man, sometimes minutes after the end of exposure, and to sensitize dogs to severe epinephrine-evoked ventricular tachyarrhythmias. To assess the duration and the rate of disappearance of myocardial sensitization, we injected 13 pentobarbital-anesthetized cats iv with 4 or 8 μg/kg epinephrine before, and at 3, 5, 8 and 10 min after, a 4-min inhalation of a 37% CCl2F2-21% O2-42% N2 mixture. Electrocardiograms and intraarterial pressures were recorded, and concentrations of CCl2F2 in arterial blood were measured by gas chromatography. Before exposure to CCl2F2, no cats had epinephrine-evoked ventricular tachyarrhythmias. After CCl2F2 inhalation, each cat developed epinephrine-evoked ventricular tachyarrhythmias. The CCl2F2-induced susceptibility to epinephrine-evoked ventricular tachyarrhythmias remained after the end of CCl2F2 inhalation, varying inversely with time and occasionally persisting as long as 10 min post CCl2F2 inhalation.

Cardiovascular responses to pentazocine and tripelennamine in anesthetized rats

Abstract 1. 1. The effects of intravenously administered pentazocine and tripelennamine, alone and in combination on cardiorespiratory functions were evaluated in anesthetized male Sprague-Dawley rats. 2. 2. Pentazocine decreased arterial blood-pressure (systolic, diastolic, mean arterial pressures without changing pulse pressure) and induced transient apnea followed initially by stimulation then depressed respiration. 3. 3. Tripelennamine produced a transient initial pressor effect followed by a depression of systolic, diastolic and mean arterial pressures. Respiratory rate was also depressed. 4. 4. When either a fixed dose of pentazocine in combination with variable doses of tripelennamine, or a fixed dose of tripelennamine with variable doses of pentazocine were injected, qualitatively similar responses were observed; namely, decreased arterial pressure and respiratory rate with an increase in pulse pressure. 5. 5. A combination of pentazocine (0.5 mg/kg) and tripelennamine (10 mg/kg) was lethal in 100% of the rats tested. 6. 6. Naloxone delayed the mortality induced by injection of single lethal combination of pentazocine and tripelennamine. 7. 7. It appears that the toxicity of a combination of pentazocine and tripelennamine is related to the paralysis of cardiorespiratory system.

Subsensitivity to noradrenaline and isoprenaline in rabbits acutely pre-treated with morphine

Abstract 1. 1. The effect of intravenously administered noradrenaline and isoprenaline on cardiovascular responses was studied in anesthetized rabbits pre-treated with morphine intravenously. 2. 2. Morphine inhibited noradrenaline-induced increases in arterial blood pressure and reflex bradycardia. 3. 3. Morphine partially antagonized isoprenaline-induced decreases in arterial pressure but did not affect the tachycardia. 4. 4. In heart tissue, morphine initially decreased and subsequently increased the uptake of tritiated noradrenaline; noradrenaline release was enhanced by morphine. 5. 5. The altered effect of sympathomimetic amines in subjects pre-treated with morphine may be due to subsensitivity of adrenergic receptors and/or due to enhanced noradrenaline uptake in the heart.