Naloxone reserves the inhibitory effects of dynorphin A on motor activity in the mouse.

Dynorphin-(1-17) (dynorphin A) significantly reduced the linear locomotion, rearing and grooming behaviors in mice using a newly devised multi-dimensional behavioral analyser. The behaviors inhibited by dynorphin A were dose-dependently antagonized by prior treatment with naloxone. The results suggest that dynorphin A-induced behavioral depression is mediated via opioid receptors in the mouse brain.