Arrest of Experimental Convulsions by Acetylcholine in the Cat. ∗

Abstract

Following a control series of experiments (15 cats) in which (1) the minimal convulsive dose of camphor monobromide, 1 (2) the total number of such dosages, (3) the total number of convulsions which could be elicited before the animal succumbed, and (4) the total amount of the drug which could be intravenously administered with 15-minute intervals between the dosages, had been established, a series of 25 cats was studied in which after establishing the minimal convulsive dose of camphor monobromide, varying dosages of acetylcholine (anhydrous solution, Chevretin-Lematte) ranging from 1:1 × 10⁻⁷ to 1:1 × 10⁻³ gm. per kilo weight were injected intravenously just before the administration of the camphor monobromide, to determine how, if at all, the convulsions would be affected.

Results. It was found: 1. That a concentration of 1 × 10⁻⁶ gm./kg. was the smallest dose of acetylcholine which would arrest the clonic convulsion following a minimal dose of camphor monobromide. 2. That while the first dosage at such a concentration would arrest clonic convulsions, a repetition of the same dosage after an interval of 15 to 30 minutes would only delay the onset of the clonic convulsions, for an interval of from 30 seconds to 10 minutes, and it was necessary to employ a greater concentration of acetylcholine before a complete arrest of clonic convulsions was again obtained. 3. A concentration of acetylcholine of 1 × 10⁻⁴ to 1 × 10⁻³ gm./kg. would always arrest a convulsion, sometimes proving lethal. (We have found the control lethal dose of this preparation of acetylcholine in the cat ranges between 0.01 and 0.09 gm./kg. 2 ) 4. While acetylcholine blocks the clonic element in such convulsions, it does not affect the element of tonic extension. 3