Acute influences of some ACTH-related peptides of fighting and adrenocortical activity in male laboratory mice

A number of corticotrophin preparations when given acutely enhanced fighting behavior, an event which may be consequent upon elevation of circulating corticosterone. A series of short ACTH analogues (ACTH 11-24, ACTH 4-10) had slight influences on circulating plasma corticosterone values and on fighting behavior. However, 20 microgram ACTH 1-10 given 12 hr before testing did increase fighting C.F. controls. As this compound only caused a slight stimulation of plasma corticosterone titers, the possibility exists of an extra-adrenal influence. One cannot, it appears, eliminate glucocorticoid influences using these preparations in the mouse. Acutely, ACTH 1-24 had virtually no influences on Animex-assessed motor activity but did enhance fighting in castrated mice maintained with either androgen or estrogen. It is tentatively concluded that the ACTH influences on aggression in the mouse are partially mediated via glucocorticoid influences on the CNS combined with an extra adrenal influence of part of the ACTH molecule. A possible reason for the differing acute and chronic influences of ACTH on fighting in mice is presented.