In view of the co-localization of spinal δ- and κ-opioid receptors, we have investigated the interaction of selective opioid receptor agonists and antagonists in the spinal cord of mice in order to determine if these receptors are organized as heteromers. The finding that norbinaltorphimine (κ) antagonized [D-Pen2,5]enkephalin (δ1), but not deltorphin II (δ2), strongly suggests that the putative δ1-subtype is a δ-κ heteromer. Studies with selective opioid receptor (ant)agonists support this conclusion.
Bibliographical noteFunding Information:
This work was supported by the National Institute on Drug Abuse research grant R37 DA01533. The animal protocols used in these experiments were approved by the University of Minnesota Institutional Animal Care and Use Committee (IACUC).
- δ-Opioid receptor
- δ-κ Heteromer