Metrazol Convulsions and Their Relation to the Epileptic Attack. ∗

Abstract

The convulsions produced by the intravenous injection of metrazol (pentamethylentetrazol) as a therapeutic agent in schizophrenia, were recorded by means of normal and ultra-high-speed motion pictures and by electromyograms. The electromyograms of the activity of antagonistic muscles were recorded simultaneously by 2 matched amplifier systems which operated crystal actuated ink-writing recorders.

The typical metrazol seizure in man is composed of 3 stages: the first clonic stage, the tonic stage and the second clonic stage. The nature of the clonus is entirely different in the 2 clonic stages. As seen from the films and the electromyograms the clonus of the first clonic stage is the result of the alternating contraction of agonistic and antagonistic muscle groups; 2 to 4 of these 2-phase movements occurring per second. The second clonic stage is the result of an alternation between simultaneous contraction and relaxation of all muscle groups. It represents an alternating disappearance and reappearance of the continuous innervation which is present in the tonic stage. The change between contraction and relaxation is very rapid at the beginning of the second clonic stage, 12 to 14 contractions occurring per second. The movements gradually become slower and coarser. Towards the end of the second clonic stage only 1 to 2 contraction seizures occur per second and finally complete relaxation follows as is evidenced by a complete absence of muscle action potentials in the electromyogram.

The tonic stage, which in the electromyogram shows simultaneous high potentials in all muscles, represents a state similar to decerebrate rigidity. The movements of the second clonic stage correspond to an intermittent innervation of the same characteristics which were continuously'present during the tonic stage. The second clonic stage, therefore, should be.