Effects of a Single Injection of Corticotropin (ACTH) on Ammonium Ion and Acetylcholine Content of the Brain

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Abstract
A single injn. of ACTH induces an increase of the electrical activity of the brain consisting of increased voltage of the brain waves, occasional spiking, and paroxysmal runs of low-frequency high-voltage waves. A single injn. of ACTH induced in less than 30 sec. an increase of the ammonium ion content of the brain. Within 5 min. the increase averaged 60%. The ammonium ion content returned to normal levels within 30 min. and decreased by 30% within 1 hr. A single injn. of ACTH induced an increase of the acetylcholine content of the brain in less than 30 sec. Within a few mins. a peak value was reached (an avg. of 40%) and the acetylcholine content returned to normal levels in less than 30 min. The results imply that the paroxysmal runs of low-frequency brain waves were induced by the increase of the ammonium ion content of the brain. The other electrical changes were induced by the increase of the acetylcholine content of the brain. These changes are effected through an extra-adrenal mechanism. Prolonged admn. of ACTH to rats in relatively high concns. induces a decrease of the electrical activity of the brain. This change is mainly due to a shift within the brain in the electrolytes, including an increased Na content in the presence of an acetylcholine content within normal limits. These changes are mediated mainly through the adrenal gland.