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Brain Res. 1989 Jan 2;476(1):102-9.

Mu-type opioid receptors in rat periaqueductal gray-enriched P2 membrane are coupled to guanine nucleotide binding proteins.

Author information

1
Department of Pharmacology, University of California, San Francisco 94143.

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 presumably associated with mu-type opioid receptors have been detected in rat PAG-enriched P2 membrane. In the present study the signal transduction mechanism of mu-type opioid receptors in the PAG was examined utilizing both in vitro radioligand binding and GTPase assays. The non-hydrolyzable guanine triphosphate (GTP) analog guanyl-5'-yl beta-gamma-imidodiphosphate (GppNHp) inhibited specific high affinity [3H][D-Ala2,N-MethylPhe4,Glyol5]enkephalin (DAGO) binding in rat PAG-enriched P2 membrane in a dose-dependent manner. DAGO stimulated total GTPase activity in rat PAG-enriched P2 membrane in a saturable, dose-dependent, ligand-selective, stereoselective, and naloxone-reversible manner. This DAGO stimulation of total GTPase activity was also dependent on Na+ and Mg2+, and was abolished by pertussis toxin pretreatment of the membrane. Overall these data suggest that mu-type opioid receptors in the PAG are coupled to guanine nucleotide binding proteins (G proteins).

PMID:
2536574
DOI:
10.1016/0006-8993(89)91541-2
[Indexed for MEDLINE]

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