Opioid peptide receptor studies. 10. Nor-BNI differentially inhibits kappa receptor agonist-induced G-protein activation in the guinea pig caudate: further evidence of kappa receptor heterogeneity
| Autor: | S O, Heyliger, C, Jackson, K C, Rice, R B, Rothman |
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| Rok vydání: | 1999 |
| Předmět: |
Pyrrolidines
Dose-Response Relationship Drug Receptors Opioid kappa Guinea Pigs Benzeneacetamides Receptors Opioid mu Brain Enkephalin Ala(2)-MePhe(4)-Gly(5) In Vitro Techniques Naltrexone Peptide Fragments Rats Benzodiazepines Inhibitory Concentration 50 GTP-Binding Proteins Guanosine 5'-O-(3-Thiotriphosphate) Receptors Opioid delta Animals Caudate Nucleus Peptides Somatostatin Oligopeptides |
| Zdroj: | Synapse (New York, N.Y.). 34(4) |
| ISSN: | 0887-4476 |
| Popis: | There is strong evidence supporting the existence of multiple kappa receptors. Previous studies proposed that U69,593 and (+)-tifluadom act on different kappa receptor subtypes, kappa(1) (kappa(1)) and kappa(2) (kappa(2)), respectively. In this study, we investigated the effects of the kappa selective antagonist nor-binaltorphimine (Nor-BNI) on U69,593- and (+)-tifluadom-induced receptor-mediated stimulation of [(35)S]-GTP-gamma-S binding in the guinea pig caudate. The IC(50) value of Nor-BNI in the presence of a stimulating concentration of U69,593 (1 microM) was 0.19+/-0.02; while the IC(50) for Nor-BNI in the presence of (+)-tifluadom (1 microM) was 13.9+/- 1.62 nM. The mu-opioid receptor antagonist CTAP (10,000 nM) significantly reduced (+)-tifluadom-stimulated [(35)S]-GTP-gamma-S binding in rat brain sections and guinea pig brain membranes, indicating that (+)-tifluadom has mu agonist activity. Under conditions in which the mu agonist activity of (+)-tifluadom was blocked by 1000 nM CTAP the Ki value for Nor-BNI for inhibition of U69,593-stimulated [(35)S]-GTP-gamma-S binding was 0.036+/-.004 nM, whereas, its Ki value for the (+)-tifluadom-stimulated [(35)S]-GTP-gamma-S binding was 0.27+/-.015 nM. These results suggest that (+)-tifluadom and U69,593 activate pharmacologically different receptors. This study provides functional evidence in support of kappa receptor heterogeneity. |
| Databáze: | OpenAIRE |
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