THE RELATION BETWEEN DRUG ACTION AND THE CALCIUM-POTASSIUM RATIO IN STRIATED MUSCLE

¹ From the National Institute for Medical Research, Hampstead, London, N. W. S

Reduction of the calcium ion content of the fluid surrounding the rectus abdominis muscle of the frog greatly sensitizes the response of this muscle to stimulation by potassium ions. The response to acetylcholine is also potentiated, but not to the same degree.

The addition of guanidine or veratrine to the fluid bathing the muscle causes a similar change in the reaction evoked by potassium ions, and the effects of both of these drugs can be counteracted by calcium ions.

These factors must be considered in the analysis of the alterations in excitability and activity of both muscle and nerve fibres in pathological states such as parathyroid tetany, and in those resulting from the action of certain drugs.