Abstract
The present study was performed to explore the involvement of opioid receptors in the calcitonin gene-related peptide 8-37 (CGRP8-37, an antagonist of CGRP receptor)-induced inhibition of the activity of wide-dynamic-range (WDR) neurons in the spinal dorsal horn of rats. Extracellular recording was performed with a multibarrelled glass micropipette, and the chemicals were delivered by micro-iontophoresis. The discharge frequency of WDR neurons was evoked by subcutaneous electrical stimulation applied to the ipsilateral hindpaw. Iontophoretic application of CGRP8-37 by an ejection current of 160 nA induced significant inhibition of the discharge frequency of WDR neurons. The inhibitory effect of CGRP8-37 on the activity of WDR neurons was attenuated by later iontophoretic application of the opioid antagonist naloxone. Furthermore, the effect of CGRP8-37 was attenuated by either iontophoretic application of the kappa-receptor antagonist nor-binaltorphimine (nor-BNI) or the mu-receptor antagonist beta-funaltrexamine (beta-FNA) but not by the delta-receptor antagonist naltrindole. The results indicate that kappa- and mu-opioid receptors on the membrane of WDR neurons are involved in the modulation of CGRP8-37-induced antinociception in dorsal horn of the spinal cord in rats.
Copyright 2004 Wiley-Liss, Inc.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Action Potentials / drug effects
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Action Potentials / physiology
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Afferent Pathways / drug effects
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Afferent Pathways / metabolism
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Animals
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Calcitonin Gene-Related Peptide / pharmacology*
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Calcitonin Gene-Related Peptide Receptor Antagonists
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Cell Membrane / drug effects
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Cell Membrane / metabolism
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Electric Stimulation
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Male
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Narcotic Antagonists / pharmacology
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Neural Inhibition / drug effects
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Neural Inhibition / physiology*
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Nociceptors / drug effects
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Nociceptors / metabolism*
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Pain / drug therapy
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Pain / metabolism*
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Pain / physiopathology
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Peptide Fragments / pharmacology*
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Posterior Horn Cells / drug effects
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Posterior Horn Cells / metabolism*
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Rats
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Rats, Wistar
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Receptors, Calcitonin Gene-Related Peptide / metabolism
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Receptors, Opioid / drug effects
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Receptors, Opioid / metabolism*
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Receptors, Opioid, delta / antagonists & inhibitors
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Receptors, Opioid, delta / metabolism
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Receptors, Opioid, kappa / antagonists & inhibitors
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Receptors, Opioid, kappa / metabolism
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Receptors, Opioid, mu / antagonists & inhibitors
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Receptors, Opioid, mu / metabolism
Substances
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Calcitonin Gene-Related Peptide Receptor Antagonists
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Narcotic Antagonists
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Peptide Fragments
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Receptors, Calcitonin Gene-Related Peptide
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Receptors, Opioid
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Receptors, Opioid, delta
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Receptors, Opioid, kappa
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Receptors, Opioid, mu
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calcitonin gene-related peptide (8-37)
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Calcitonin Gene-Related Peptide