EFFECTS OF 10-METHOXYDESERPIDINE ON THE ECG CHANGES INDUCED BY VASOPRESSIN IN UNANESTHETIZED RABBIT

Abstract

Since the report of hypotensive effect without central depression of 10-methoxydeserpidine (1), several investigators have studied the mode of its action. Mir and Lewis (2) have demonstrated the gradually developing fall of blood pressure following 10-methoxydeserpidine in cats, rabbits and rats. However, unlike reserpine, 10-methoxydeserpidine does not produce significant depletion of brain and heart noradrenaline in mice (3). Recently, Higuchi et al. (4) and Toda et al. (5) in this laboratory have reported that the intravenous or intracarotid injection of 5 to 10 mg/kg of 10-methoxydeserpidine in rabbits produces considerable depletion of catecholamines in the brain, heart and adrenal glands. The latter authors (5) have further shown that the intravenous injection of 10 mg/kg of 10-methoxydeserpidine to rabbits results in a sustained rise of the skin temperature of the ear without modifying the rectal temperature, and that 1 mg/kg of reserpine produces a similar but longer-lasting rise of the ear skin temperature with a significant fall of the rectal one. They suggested that the skin temperature rise might be due to an increased blood flow in the ear. The earlier observation by Guthrie (6) that the inhalation of amyl nitrite, a potent coronary vasodilator, in man produced a flushing of the skin with a temperature rise and a blood flow increase in the neck and face indicates a resemblance of the effects of amyl nitrite to those of 10-methoxydeserpidine and reserpine.
The ECG changes in rabbits and dogs following the posterior pituitary extract were described by Melville (7), Hecht and Nadel (8), and Gruber and Kountz (9). They observed an elevation of ST level, and increase in height of T wave and the ventricular extrasystole with a concomitant blood pressure rise, and ascribed these ECG changes to the anoxia of the heart secondary to the coronary vasoconstriction.
The present report describes the effect of 10-methoxydeserpidine on ECG changes in rabbits following the intravenous administration of vasopressin in an attempt to confirm the coronary vasodilating action of 10-methoxydeserpidine.