Previous studies delineated two classes of δ binding sites: a δ binding site not associated with the opioid receptor complex, termed the δncx site, and a δ site associated with the opioid receptor complex, termed the δcx site (for review see (1)). More recent studies resolved two δcx binding sites in rat brain termed δcx-1 and δcx-2 (2). Pretreatment of membranes with the δ-selective acylating agent (+)-trans-SUPERFIT depletes membranes of the δncx binding site which permits selective labeling of the δcx binding sites with [3H]DADLE (3). Ligand-selectivity studies of the non-peptide δ agonist, BW373U86, its enantiomers and related compounds showed that these drugs have higher affinities for δ sites than μ sites (4,5). This study determined the selectivity of these compounds for the two δcx binding sites. The data indicate that (+)-4-[(αR)-α((2S,5R)-4-allyl-2,5-dimethyl-1- piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC80) and deltorphin-II are highly selective for δcx-2 binding site (2758-fold and 700-fold respectively). In contrast, morphine is selective for δcx-1 binding site (78-fold).
ASJC Scopus subject areas
- Clinical Biochemistry
- Cellular and Molecular Neuroscience