Behavioral effects of the [beta]-endorphin fragment 2-9

Abstract

The non-opiate β-endorphin (βE) fragment des-Tyr-α-endorphin (βE 2–16) delays extinction of pole jumping avoidance behavior and potentiates apomorphine-induced stereotyped sniffing. Structure-activity relationship studies revealed that the active moiety mediating these psycho-stimulant effects resides in the sequence βE 2–9. The interaction between βE 2–9 and apomorphine was also present following intrastriatal injection of both substances. These data provide evidence for a selective interference of the fragment βE 2–9 with brain mechanisms, which can be distinghuised from the opiate-and neuroleptic-like activity of β-endorphin fragments. This further demonstrates the importance of β-enndorphin and its fragments for modulation of behavioral processes.