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.
- δ-Opioid receptor
- δ-κ Heteromer