Effects of Various Concentrations of Adrenocorticotrophic Hormone on Electrical Activity of Brain and on Sensitivity to Convulsion-Inducing Agents

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Abstract
-The effects of admn. of ACTH in various concns. and for a different length of time on the electrical activity of the brain and on the sensitivity of rats to the convulsion-inducing effects of penta-methylene tetrazol were ascertained. Prolonged admn. of ACTH induced a decrease of sensitivity of animals to pentamethylene tetrazol. Single injns. of ACTH and repeated injns. of ACTH made within a few min. induced an increased electrical activity of brain. This change consisted of an increase of voltage, occasional spiking, paroxysmal runs of low-frequency high-voltage waves and lowering of convulsion threshold of pentamethylene tetrazol. ACTH induced similar effects in nonoperated, hypophysectomized, adrenalectomized, and Na-injected non-operated animals. It is suggested that ACTH modifies the activity of brain by at least 2 mechanisms. Prolonged admn. of ACTH in relatively large concns. induces a decrease of the electrical activity due mainly to shift in electrolytes; admn. of ACTH in either a single injn. or injns. repeated within a short period of time induces an increased activity and hyperexcitability of the brain by a mechanism that is not dependent on the presence of the adrenal cortex.