In contrast to the pharmacological studies implicating delta-opioid receptor subtypes, cloning studies have identified only a single cDNA encoding a delta receptor, DOR-1. Antisense studies have established the importance of DOR-1 in delta analgesia in mice. Antisense mapping extends this approach to include oligodeoxynucleotides which are targeted against each of the exons of the gene. Five different antisense oligodeoxynucleotides based upon the three DOR-1 exons all block both spinal and supraspinal analgesic actions of the delta2 ligand [D-Ala2,Glu4]deltorphin, consistent with the suggestion that DOR-1 encodes the delta2 receptor. At the spinal level, [D-Pen2,D-Pen5]enkephalin (DPDPE) acts also acts through delta2 receptors and all the antisense probes block spinal DPDPE analgesia. However, supraspinally only the two antisense probes targeting exon 3 block DPDPE analgesia. The remaining three antisense probes based upon exons 1 and 2 are inactive. Thus, the delta receptors responsible for spinal and supraspinal DPDPE analgesia can be discriminated at the molecular level by antisense mapping.