Abstract

1. The ammonium ion content of the brain remained within normal limits during the preconvulsive phase induced by physostigmine salicylate arid pentyl-enetetrazole and increased up to 900 per cent during the preconvulsive phase induced by ammonium chloride.

2. Convulsions were induced by administration of ammonium chloride only when the ammonium ion content of the brain exceeded ten times the control values.

3. The ammonium ion content of the brain increased during convulsions induced by various agents.

4. The changes in the electrical activity of the brain during the preconvulsive phase consisted of paroxysmal bursts of low frequency waves in the presence of an increase of the ammonium ion content of the brain (and of other changes in the absence of such increase).

5. Convulsions coincided with similar electrical activity of the brain (high voltage fast activity) regardless of whether or not the ammonium ion content of the brain increased significantly.

6. It is concluded that an accumulation of the ammonium ion in the brain is the result of increased cerebral activity and is not necessarily the factor initiating convulsions (i.e. convulsions induced by pentylenetetrazole, physostigmine salicylate). One of the physiological effects of the accumulation of ammonium ion is to contribute to the termination of convulsions.