Abstract
Opioid receptors have been demonstrated by light microscopic techniques in fine cutaneous nerves in naive animals. The present study extends these findings by showing that 29 and 38% of unmyelinated cutaneous sensory axons can be immunostained for mu- or delta-opioid receptors respectively. Local cutaneous injection of DAMGO, a mu-opioid ligand, ameliorates the nociceptive behaviors caused by local cutaneous injection of glutamate, a purely nociceptive chemical stimulus showing that the mu-receptors are functional. By contrast the delta-opioid ligand [2-D-penicillamine, 5-D-penicillamine]enkephalin (DPDPE) had no effect on these behaviors. These findings indicate a wider function for opioid receptors in naive animals than previously envisioned.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Axons / drug effects
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Axons / metabolism*
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Axons / ultrastructure
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Behavior, Animal / drug effects
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Behavior, Animal / physiology
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Dose-Response Relationship, Drug
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Glutamic Acid / pharmacology
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Immunohistochemistry
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Inflammation / pathology
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Male
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Narcotic Antagonists
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Neurons, Afferent / drug effects
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Neurons, Afferent / metabolism*
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Neurons, Afferent / ultrastructure
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Peripheral Nervous System / cytology
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Peripheral Nervous System / drug effects
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Peripheral Nervous System / metabolism*
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Rats
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Rats, Sprague-Dawley
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Receptors, Opioid / agonists
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Receptors, Opioid / metabolism*
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Receptors, Opioid, delta / agonists
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Receptors, Opioid, delta / antagonists & inhibitors
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Receptors, Opioid, mu / agonists
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Receptors, Opioid, mu / antagonists & inhibitors
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Receptors, sigma / agonists
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Receptors, sigma / antagonists & inhibitors
Substances
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Narcotic Antagonists
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Receptors, Opioid
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Receptors, Opioid, delta
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Receptors, Opioid, mu
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Receptors, sigma
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Glutamic Acid