Physiological Effects of Some Thio-Esters of Choline

Abstract

The effects on blood pressure and respiration produced in cats and dogs under morphine-urethane, nembutal and chloralose anesthesias, by intravenous injections of thio-acetyl choline chloride, thio-acetyl-gamma-homo-choline chloride and thio-acetyl-beta-methyl choline chloride have been observed and recorded.∗ Eighteen animals (10 cats and 8 dogs) have been used in these experiments. Records were taken of the results of over 200 injections, of which approximately one-third was of each of the 3 compounds. The results of the administration of each compound were constant.

Thio-acetyl-choline chloride and thio-acetyl-gamma-homo choline chloride are almost identical in their effects. Immediately following injection the blood pressure falls slightly, then rises rapidly to 60 to 90 mm Hg above the normal level. During this rapid rise the heart rate increases but upon reaching the peak pressure the rate slows and large vagal beats appear. The duration of this bradycardia varies from one to 5 minutes depending upon the amount of the compound injected. During this period the blood pressure gradually falls to normal, which level is reached in 2 to 10 minutes. Hyperpnea of short duration immediately follows injection. This hyperpnea is followed by depression with gradual return to normal.

Thio-acetyl-beta-methyl choline chloride produces a moderate depressor action but has no effect upon the respiration. B.P. falls 30-50 mm Hg and is not accompanied by changes in heart rate.

The minimum effective dose is of the order of .016 mg/kg. When larger dosages are used (.5-1 mg/kg) the animals rapidly pass into a fatal apnea.

Atropine sulphate abolishes neither the pressor response nor the hyperpnea caused by thio-acetyl choline chloride and thio-acetyl-gamma-homo choline chloride, but eliminates the bradycardia. The depressor action of thio-acetyl-beta-methyl choline chloride is abolished by atropine. Physostigmine does not augment the action of any of these compounds