Morphine Inhibits Resting Respiration, but It Attenuates Reflexive Respiratory Suppression in Anesthetized Cat through κ-Receptor

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Author(s)

Abstract

Noxious stimulation of thin-fiber muscular afferents induces a reflexive respiratory suppression that we call "poststimulus respiratory suppression." In anesthetized, vagotomized, paralyzed, and artificially ventilated cats, morphine depressed the level of resting respiration (inhibitory effect on resting respiration) and attenuated the magnitude of the poststimulus respiratory suppression (excitatory effect on the reflexively modified respiration). These two kinds of morphine effects were antagonized by naloxone, suggesting the participation of opioid receptors. To clarify the opioid receptor subtypes responsible for these effects of morphine, three type-selective opioid antagonists—naltrindole (δ antagonist), β-funaltrexamine (μ antagonist), and Mr2266 (κ antagonist)—were tested. The morphine-induced depression in the resting respiration was antagonized by pretreatment with the κ antagonist, not with the μ or δ antagonist. Furthermore, the morphine-induced attenuation in the magnitude of the poststimulus suppression was also blocked by the κ antagonist, but not by the μ or δ antagonist. In conclusion, (1) morphine inhibits resting respiration, but it attenuates the magnitude of the poststimulus respiratory suppression; (2) both these morphine effects are mediated by κ opioid receptors. The possibility that the κ<sub>3</sub> receptor, one of the κ receptors subtypes, mediates the two kinds of morphine effects has been discussed.<br>

Journal

  • The Japanese Journal of Physiology

    The Japanese Journal of Physiology 50(6), 615-624, 2000-12-01

    THE PHYSIOLOGICAL SOCIETY OF JAPAN

References:  40

Cited by:  1

Codes

  • NII Article ID (NAID)
    10008292488
  • NII NACSIS-CAT ID (NCID)
    AA00691224
  • Text Lang
    ENG
  • Article Type
    Journal Article
  • ISSN
    0021521X
  • NDL Article ID
    5706372
  • NDL Source Classification
    ZS8(科学技術--医学--解剖学・生理学・生化学)
  • NDL Call No.
    Z53-D40
  • Data Source
    CJP  CJPref  NDL  J-STAGE 
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