EFFECT OF PICROTOXIN, STRYCHNINE AND METRAZOL (PENTAMETHYLENETETRAZOLE) ON THE ACTION OF PROSTIGMINE AND CURARE ON THE NEUROMUSCULAR JUNCTION

¹ Department of Pharmacology and Biological Chemistry, Catholic University of Chile, Santiago de Chile, Chile

Studies are carried out in cats anesthetized with Nembutal in order to observe the effects on the indirectly stimulated quadriceps muscle when the animal has received prostigmine under curarization. The following observations are made.

Picrotoxin has practically no effect. What little it does have seems to be a feeble reinforcement of the effect of prostigmine and of curare (fig. 1 and Section A of Results).

Strychnine has a complex reaction. For a few seconds it reinforces the action of curare and of prostigmine and then produces a moderate decurarization or a violent deprostigminization (fig. 2 and Section B of Results).

Metrazol weakly reinforces the action of prostigmine and behaves as a decurarizing drug (fig. 3 and Sec. C of Results).

The behaviour of these three substances is discussed in the light of our present knowledge of the theory of neural transmission. The conclusion is drawn that the behavior of picrotoxin and strychnine cannot be explained by the classical theory of the two thresholds of acetylcholine, whereas metrazol can be looked upon as a neuromuscular depressant in that it elevates the acetylcholine thresholds.