Delta-opioid receptor binding sites in rodent spinal cord.
1. The delta-opioid receptor agonist [D-Pen2,D-Pen5]enkephalin showed an antinociceptive effect in the mouse tail-flick test, following intrathecal administration. This action was reversed by naloxone and by the selective delta-opioid receptor antagonist ICI 174864. 2. High affinity, saturable binding of [3H]-[D-Pen2,D-Pen5]enkephalin has been demonstrated in spinal cord homogenates from guinea-pig, hamster, rat and both adult and young (18-20 g) mice. The binding was shown by autoradiography to be concentrated in the superficial laminae of the dorsal horn. 3. Competition studies confirmed that the binding of [3H]-[D-Pen2,D-Pen5]enkephalin was to the delta-opioid site. However, anomalies were seen with displacement assays using mu-ligands, which may suggest some common high affinity site for delta- and mu-opioid receptor agonists in the spinal cord. 4. The results add further evidence for a role of the delta-opioid receptor in spinally-mediated antinociception.
Traynor
J R
JR
Department of Chemistry, Loughborough University, Leics.
Hunter
J C
JC
Rodriguez
R E
RE
Hill
R G
RG
Hughes
J
J
D000700:Analgesics; D000818:Animals; D001345:Autoradiography; D001667:Binding, Competitive / Q000187:drug effects; D006224:Cricetinae; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007278:Injections, Spinal; D008297:Male; D008647:Mesocricetus; D051379:Mice; D008815:Mice, Inbred Strains; D009270:Naloxone / Q000494:pharmacology; D011597:Psychomotor Performance / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000187:drug effects; D011957:Receptors, Opioid / Q000378:metabolism*; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D013116:Spinal Cord / Q000378:metabolism*
D000700:Analgesics; D004745:Enkephalins; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D009270:Naloxone; D020881:Enkephalin, D-Penicillamine (2,5)-