OBSERVATIONS ON THE EFFECT OF CALCIUM ON THE ACTION OF COCAINE

¹ From the Biological Laboratory, Cold Spring Harbor, Long Island, New York

1. Cocaine injected intravenously into normal cats produced no effect on intestinal motility in most experiments, but occasionally caused inhibition and more rarely stimulation.

2. From the results of experiments with cocaine after the administration of ergotamine or atropine it was concluded that it stimulated the parasympathetic and the sympathic ending.

3. Cocaine usually stimulated intestinal motility when blood calcium was reduced, its effect being still greater if ergotamine as well as oxalate was given before; but cocaine depressed the intestine after intravenous injections of CaCl₂.

4. Small amounts of cocaine increased the blood pressure in 90 per cent of the experiments when blood calcium was normal; and in 44 per cent when calcium was lowered by oxalate.

5. The pressor action of cocaine was decreased and sometimes reversed when blood calcium had been reduced. This occurred especially when it was given after oxalate and ergotamine.

6. Cocaine after oxalate and ergotamine also depressed the circulation in atropinized cats. The effect was, therefore, due to its action on cardiac muscle. Calcium depletion of the blood thus transformed cocaine from a cardiac stimulant into a cardiac depressant. After the intravenous injection of CaCl₂ cocaine raised the blood pressure.

7. Depression of the respiration by cocaine was decreased by the previous administration of oxalate or when blood calcium was lowered by removal of the parathyroids.