Tyr-ACTH (4-9) is a behaviorally active peptide. Tyr-ACTH (4-9) can be used for research of learned behavior extinction in the rat[1].
References
[1] Bickel U, et al. The behaviorally active peptide ACTH 4-10: measurement in plasma and pharmacokinetics in man. Eur J Clin Pharmacol. 1988;35(4):371-7. DOI:10.1007/BF00561367