THE EFFECTS OF ALIPHATIC SYMPATHOMIMETIC AMINES ON CARDIAC AUTOMATIC TISSUE IN DOGS UNDER CYCLOPROPANE

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Abstract
The effect of 17 straight chain sympathomimetic amines was studied under cyclopropane anesthesia. The straight chain amines were compared with standard test doses of epinephrine (0.01 mg./kg.). Epinephrine pressor equivalents were calculated from data of Chen, based on his expts. with pithed dogs. Each drug was diluted to 5 ml. with distilled water and injd. intraven. at an even rate within a period of 50 sec. Electrocardiographs at frequent intervals were used to determine cardiac rates and irregularities. Since the pressor equivalent of 2-methylamino-6-hydroxy-6-methylheptane (aranthol) has not been determined, a dose of 10 mg./kg. was selected as maximum. In this dosage aranthol stimulated the cardiac automaticity centers to a lesser degree than epinephrine; it caused no ventricular fibrillation, but caused ventricular tachycardia under cyclopropane. 5 mg./kg. was the min. dosage for good pressor response; 8 of 20 dogs were entirely free of ventricular irregularities with this dose. The min. effective dose of 2-aminoheptane (tuamine) was 1.5 mg./kg.: 2 of 6 dogs were free of ventricular irregularities with this dose. Of the 17 amines investigated, 6 (2-amino-1-cyclohexyl-propane, 2-amino-5-methylhexene-5, 2-amino-3,6-dimethylheptane, 2-methylamino-l-cyclopentyl-propane, 3-aminoheptane, and 2-aminooctane) did not produce ventricular irregularities in doses equivalent to 0.01 mg./kg. epinephrine. Several others (2-amino-1-cyclopentylethane, 1 -amino -3 -methylbutane, 1-amino-3,4-dimethylpentane, 2-amino-4-methylhexane, 2-amino-5-methylhexane, 1-amino-3-methylheptane, 2-amino-6-methylheptene-5, 2-aminoheptane, and 2-methylamino-6-hydroxy-6-methylheptane) did produce ventricular stimulation in comparable doses.

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