In vivo fate of a behaviorally potent ACTH 4-9 analog; evidence for its specific uptake in the brain septal area

The effects of ACTH-like neuropeptides on conditioned avoidance behavior and their tentative central sites of action are reviewed. The in vivo fate of the [3H]-ACTH 4-9 analog after various routes of peripheral administration in mice and rats are described, in particular, the uptake of intact peptide in the brain is emphasized, since ACTH-like neuropeptides elicit their behavioral activities by directly affecting the central nervous system. Subsequently, the metabolic profiles of the ACTH 4-9 analog in plasma and brain tissue are reported. The distribution of the [3H]-ACTH 4-9 analog throughout the rat brain is studied after intraventricular injection to allow detection in small brain areas and nuclei and to limit (peripheral) proteolysis. Finally, the effects of increased and decreased circulating levels of both ACTH-like peptides and structurally non-related but behaviorally active neuropeptides on the central distribution profile of intraventricularly injected [3H]-ACTH 4-9 analog are reviewed