ACTH-(11-24) antagonizes ACTH-(1-24)-induced behavioral syndrome.

The possible involvement of the ACTH-(11-24) fragment on the stretchings, yawnings and penile erections induced by the intracerebroventricular injection of ACTH-(1-24) in rats, was studied. The results indicate that this C-terminal fragment is devoid of any behavioral activity, but inhibits the behavioral syndrome induced by ACTH-(1-24). This suggests that the fragment-(11-24) of the ACTH molecule may contain or represent an address sequence for brain ACTH receptors and may be involved in the termination of the behavioral response to melanocortins.