EFFECT OF CHLOROFORM AND ETHER ON THE SENSITIVITY OF MUSCLE TO ACETYLCHOLINE

¹ From the Department of Pharmacology, Cornell University Medical College, New York

1. The effect of chloroform and ether on the response of the rectus abdominis muscle of frog to acetylcholine was investigated.

2. These drugs in low concentrations increase the response of the muscle to acetylcholine (chloroform from 0.0025 to 0.03 cc. per cent; ether from 0.5 to 1.5 cc. per cent).

3. Higher concentrations decrease the response of the muscle to acetylcholine (chloroform from 0.03 cc. per cent; ether from 1.5 cc. per cent).

4. Still higher concentrations cause contracture (chloroform from 0.16 cc. per cent; ether more than 3.7 cc. per cent).

5. Physostigmine potentiates the response of deeply chloroformed muscles to acetylcholine.

6. Chloroform and ether potentiate the response of fully eserinized muscles to acetylcholine.

7. Chloroform and ether even in high concentration are not able to counteract the effect of atropine in inhibiting the effect of acetylcholine.

8. Atropine does not modify chloroform and ether contracture.

9. These results indicate that chloroform and ether increase the excitability of the parasympathetic nervous system both by inhibiting the destruction of acetylcholine by choline esterase and by increasing the sensitivity of the effector organs to acetylcholine.

10. The contracture caused by chloroform and ether is probably the result of processes which do not involve acetylcholine.

11. The difference in the parasympathetic effects of chloroform and ether during anesthesia may be explained by the difference in concentrations required to stimulate the parasympathetic nervous system and the relative lethal concentrations in the tissues.