| Abstract: |
Both [3H]U69,593 alone and [3H]ethylketocyclazocine (EKC) in the presence of μ and δ blockers ([D-Ala2,MePhe4, Glyol5] enkephalin (DAMGO) and [D-Pen2,D-Pen5]enkephalin (DPDPE)) label κ receptors in the guinea pig cerebellum. Dynorphin A(1-17) and nor-binaltorphimine (nor-BNI) potently competed the binding of both radioligands with Hill coefficients of approximately unity, strongly supporting a κ classification of binding. However, saturation studies revealed that the Bmax for [3H]EKC binding was 45% greater than that for [3H]U69593, suggesting that [3H]EKC might be labeling more than one site. Although nonlinear regression analysis of dynorphin A(1-17) and nor-BNI competition of [3H]EKC binding best fit the curves with a one site model, competitions by dynorphin B, dynorphin A(1-9) and α-neoendorphin revealed Hill coefficients less than unity and were best fit to a two site model. Kinetic analysis also supported [3H]EKC binding heterogeneity. Together, these studies imply that under these conditions [3H]EKC labels more than one site in the guinea pig cerebellum. The sensitivity of all specific [3H]EKC binding to the selective κ ligands dynorphin A(1-17) and nor-BNI indicates that both component are κ while the differing sensitivities of dynorphin B, α-neoendorphin and dynorphin A(1-9) for these components support our previous hypothesis of κ1a and κ1b binding subtypes. © 1991. |
| Keywords: |
controlled study; nonhuman; animal; animal tissue; cerebellum; haloperidol; binding sites; ligand binding; binding competition; in vitro; naloxone; opiate receptor; enkephalin[2,5 dextro penicillamine]; tritium; pyrrolidines; receptor subtype; binding, competitive; n allylnormetazocine; pentazocine; 3,4 dichloro n methyl n [2 (1 pyrrolidinyl)cyclohexyl]benzeneacetamide methanesulfonate; naloxone benzoylhydrazone; drug concentration; nalbuphine; dynorphin a; enkephalin; ethylketazocine; kappa opiate receptor; radioligand; guinea pig; enkephalin[2 dextro alanine 4 methylphenylalanine 5 glycine]; binding kinetics; guinea pigs; receptors, opioid; norbinaltorphimine; alpha neoendorphin; priority journal; article; nalorphine; receptors, opioid, kappa; support, non-u.s. gov't; support, u.s. gov't, p.h.s.; dynorphins; dynorphin b; n methyl n [7 (1 pyrrolidinyl) 1 oxaspiro[4.5]dec 8 yl]benzeneacetamide; opiate receptor affecting agent; leucine enkephalin[2 dextro serine 6 threonine]; ethylketocyclazocine; u69,593; κreceptor; 5,9 diethyl 2 (3 furylmethyl) 2' hydroxy 6,7 benzomorphan; dynorphin[1-9]; spiradoline
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