Abstract
The periaqueductal gray (PAG) region of the midbrain has been implicated in both stimulation-produced and opioid-induced analgesia. High-affinity mu-selective opioid-binding sites associated with mu type opioid receptors have been detected in rat PAG-enriched P2 membranes, and these receptors have been shown to be coupled to guanine nucleotide-binding proteins (G-proteins). In the present study the potential G-protein-mediated coupling of mu type opioid receptors to the inhibition of adenylyl cyclase was examined utilizing in vitro adenylyl cyclase assays. In the presence of Na+, opioid agonists inhibited adenylyl cyclase in a mu selective, naloxone reversible, dose dependent, and pertussis toxin sensitive manner. Overall the data suggests that mu type opioid receptors in the rat PAG are coupled to G-protein-mediated inhibition of adenylyl cyclase.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer
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Adenylate Cyclase Toxin
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Adenylyl Cyclase Inhibitors*
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Animals
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Cell Membrane / enzymology
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Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
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Enkephalin, D-Penicillamine (2,5)-
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Enkephalins / pharmacology
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GTP-Binding Proteins / physiology*
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In Vitro Techniques
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Periaqueductal Gray / physiology*
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Pertussis Toxin
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Pyrrolidines / pharmacology
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Rats
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Rats, Inbred Strains
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Receptors, Opioid / drug effects
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Receptors, Opioid / physiology*
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Receptors, Opioid, mu
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Virulence Factors, Bordetella / pharmacology
Substances
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Adenylate Cyclase Toxin
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Adenylyl Cyclase Inhibitors
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Enkephalins
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Pyrrolidines
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Receptors, Opioid
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Receptors, Opioid, mu
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Virulence Factors, Bordetella
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Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
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3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer
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Enkephalin, D-Penicillamine (2,5)-
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Pertussis Toxin
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GTP-Binding Proteins