A synthetic pepetide δ-opioid receptor agonist (Ki = 2.7 nM in rat brain homogenates); >250-fold selectivity for the δ-opioid receptor over the μ- and κ-opioid receptors in rat brain homogenates (Kis = 713 and >1,500 nM, respectively); selectively inhibits electrically-evoked contractions in mouse vas deferens over guinea pig myenteric plexus (IC50s = 4.14 and 3,000 nM, respectively); completely blocks MES-induced tonic hindlimb extension in 50% of tested rats and increases the flurothyl-induced seizure threshold by 15-20% in rats at 140 nmol; reduces formalin-induced paw licking and lifting, indicating analgesia, in rats from 1-10 μg; increases the latency to tail withdrawal in the tail-immersion test in both wild-type and δ-opioid receptor knockout mice