Differential behavioral effects of ACTH 4-10 and [D-Phe7] ACTH 4-10.

Intraventricular administration of an access of ACTH 4-10 does not interfere with the excessive grooming behavior of rats, elicited by intraventricular administration of [D-Phe7] ACTH 4-10. In an avoidance extinction paradigm, the two ACTH analogs have opposite effects. ACTH 4-10 counteracts the facilitation of extinction seen after [D-Phe7] ACTH 4-10, only under conditions that treatment with ACTH 4-10 alone results in retardation of that extinction. The data are discussed in terms of a multiple interaction of these peptides with brain function.