Recent Advances in the Search for the μ-Opioidergic System : The Antinociceptive Properties of Endomorphin-1 and Endomorphin-2 in the Mouse
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Two highly selective μ-opioid receptor agonists, endomorphin-1 (EM-1) and endomorphin-2 (EM-2), have been identified and postulated to be endogenous μ-opioid receptor ligands. The present minireview describes the antinociceptive properties with the tail-flick test of these two ligands given intracerebroventricularly (i.c.v.) and intrathecally (i.t.) in ICR mice. EM-1 or EM-2 given i.c.v. or i.t. dose-dependently produce antinociception. These antinociceptive effects induced by EM-1 and EM-2 given i.c.v. or i.t. are selectively mediated by the stimulation of μ-, but not δ- or κ-opioid receptors. Like other μ-opioid agonists morphine and DAMGO ([<sc>D</sc>-Ala2,NMePhe4,Gly5-ol]enkephalin), EM-1 and EM-2 given i.c.v. activate descending pain controls by the releases of noradrenaline and 5-HT and subsequently act on α2-adrenoceptors and 5-HT receptors, respectively, in the spinal cord to produce antinociception. However, the antinociception induced by EM-2 given i.c.v. or i.t. also contain an additional component, which is mediated by the release of dynorphin A(1 – 17) acting on κ-opioid receptors at the supraspinal and spinal sites. In addition, the antinociception induced by EM-2 given i.c.v. contains another component, which is mediated by the release of Met-enkephalin acting on δ2-opioid receptors in the spinal cord. It is proposed that there are two subtypes of μ-opioid receptors,which are involved in EM-1- and EM-2-induced antinociception. One subtype of μ-opioid receptors is stimulated by EM-1, EM-2 and other μ-opioid agonists morphine and DAMGO; and another subtype of μ-opioid is sorely stimulated by EM-2 and is involved in the releases of dynorphin A(1 – 17) and Met-enkephalin for the production of antinociception.
- 社団法人 日本薬理学会の論文
- 2002-07-01
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関連論文
- Recent Advances in the Search for the μ-Opioidergic System : The Antinociceptive Properties of Endomorphin-1 and Endomorphin-2 in the Mouse
- Lack of μ-Opioid Receptor-Mediated G-Protein Activation in the Spinal Cord of Mice Lacking Exon 1 or Exons 2 and 3 of the MOR-1 Gene
- TRK-820, a Selective к-Opioid Agonist, Produces Potent Antinociception in Cynomolgus Monkeys
- Recent Advances in the Search for the μ-Opioidergic System : Differential Mechanism of G-Protein Activation Induced Endogenous μ-Opioid Peptides, Endomorphin and β-Endomorphin
- Evidence for the Existence of the β-Endorphin-Sensitive "ε-Opioid Receptor" in the Brain: The Mechanisms of ε-Mediated Antinociception
- Intrathecal Treatment With 6-Hydroxydopamine or 5, 7-Dihydroxytryptamine Blocks the Antinociception Induced by Endomorphin-1 and Endomorphin-2 Given Intracerrbroventricularly in the Mouse