Deltorphin C is a peptide agonist of δ-opioid receptors (Ki = 0.15 nM) that has been found in Phyllomedusa bicolor.1 It is selective for δ-opioid receptors over µ- and ?-opioid receptors. It induces δ-opioid receptor translocation from large dense-core vesicles to the cell surface and induces calcitonin gene-related peptide (CGRP) release in isolated mouse dorsal root ganglion (DRG) cells when used at concentrations of 0.1 and 1 µM, respectively, effects that can be blocked with the δ-opioid receptor antagonist naltrindole .2 Intrathecal administration of deltorphin C (0.15, 1.5, and 15 µg/animal) increases latency to withdraw in the paw pressure and tail-flick tests in rats.3
1.Erspamer, V., Melchiorri, P., Falconieri-Erspamer, G., et al.Deltorphins: A family of naturally occurring peptides with high affinity and selectivity for delta opioid binding sitesProc. Natl. Acad. Sci. USA86(13)5188-5192(1989) 2.Bao, L., Jin, S.-X., Zhang, C., et al.Activation of delta opioid receptors induces receptor insertion and neuropeptide secretionNeuron37(1)121-133(2003) 3.Labuz, D., Toth, G., Machelska, H., et al.Antinociceptive effects of isoleucine derivatives of deltorphin I and deltorphin II in rat spinal cord: A search for selectivity of delta receptor subtypesNeuropeptides32(6)511-517(1998)