Galanin Acts at GalR1 Receptors in Spinal Antinociception: Synergy with Morphine and AP-5
| Autor: | Carol S. Hayes, Tony L. Yaksh, Tamas Bartfai, Kalle Kilk, Ülo Langel, Xiao-Ying Hua, Bethany Fitzsimmons, Anthony Hofer |
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| Rok vydání: | 2003 |
| Předmět: |
Male
Agonist medicine.medical_specialty medicine.drug_class Pain Neuropeptide Galanin Galanin receptor Rats Sprague-Dawley Internal medicine medicine Animals Receptor Injections Spinal Pharmacology Analgesics Morphine Chemistry digestive oral and skin physiology Antagonist Drug Synergism Receptor Galanin Type 1 Rats Disease Models Animal Endocrinology Nociception 2-Amino-5-phosphonovalerate Spinal Cord Molecular Medicine medicine.drug |
| Zdroj: | Journal of Pharmacology and Experimental Therapeutics. 308:574-582 |
| ISSN: | 1521-0103 0022-3565 |
| DOI: | 10.1124/jpet.103.058289 |
| Popis: | The neuropeptide galanin (Gal) and its receptors (GalR1, GalR2, and GalR3) are expressed in spinal cord. We have characterized the pharmacology of the antinociceptive effects of intrathecally (i.t.) administered galanin and its analogs in the formalin test in rats, using an automated flinch detection system. Intrathecal injection of rat galanin (Gal(1-29)) or human galanin (Gal(1-30)) produced a dose-dependent inhibition of formalin-evoked flinching in phase 2, but not in phase 1. Relative potency of galanin homologs is Gal(1-29) >or= Gal(1-30) > galanin-like peptide(1-24) >or= Gal(2-11) = Gal (3-29) (an inactive analog). Galanin(1-29) and Gal(1-30) are both high-affinity agonists to GalR1/R2, whereas Gal(2-11) is a GalR2 receptor agonist. Our data suggest that i.t. galanin-produced antinociception is mediated by activation of GalR1 receptors. When comparing antinociceptive effects of i.t. Gal(1-29) to morphine and to 2-amino-5-phosphonopentanoic acid (AP-5, an N-methyl-d-aspartate antagonist), Gal(1-29) is of intermediate potency between these two analgesic agents based on the ED(50) values. An isobolographic analysis showed synergy between Gal(1-29) and morphine and between Gal(1-29) and AP-5 on the second phase. Fixed ratio dose combinations of morphine and Gal(1-29), or AP-5 and Gal(1-29) produced significantly greater antinociception than predicted from simple additivity. In summary, the present findings reveal that 1) spinal galanin produces a reliable inhibition of formalin-induced facilitated nociceptive processing, an effect possibly mediated by GalR1 receptors; and 2) galanin potentiates i.t. morphine and AP-5-induced antinociception. |
| Databáze: | OpenAIRE |
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