Abstract
The recently identified endogenous agonists on the mu-opioid-receptor (mu OR), endomorphin-1 (EM-1) and endomorphin-2 (EM-2), induce a concentration dependent inhibition of electrical field stimulation (EFS)-induced tachykinin-mediated contractions of the guinea-pig bronchus (ED50s < 10 nM for both compounds). Surprisingly, only endomorphin-1 effects could be blocked by naloxone (10 microM), whereas endomorphin-2 effects were not affected by specific antagonists for the mu-, kappa-, and delta-opioid-receptor.
MeSH terms
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Analgesics, Opioid / antagonists & inhibitors
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Analgesics, Opioid / pharmacology
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Animals
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Bronchi / drug effects
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Bronchi / physiology*
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Capsaicin / pharmacology
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Electric Stimulation
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Guinea Pigs
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In Vitro Techniques
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Male
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Muscle Contraction / drug effects*
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Naloxone / pharmacology*
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Naltrexone / analogs & derivatives
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Naltrexone / pharmacology
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Narcotic Antagonists / pharmacology
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Neurokinin A / pharmacology
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Oligopeptides / antagonists & inhibitors*
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Oligopeptides / pharmacology
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Receptors, Opioid, mu / agonists
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Receptors, Opioid, mu / physiology
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Tachykinins / pharmacology*
Substances
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Analgesics, Opioid
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Narcotic Antagonists
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Oligopeptides
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Receptors, Opioid, mu
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Tachykinins
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endomorphin 1
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Naloxone
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norbinaltorphimine
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endomorphin 2
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Naltrexone
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Neurokinin A
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Capsaicin