Inhibition of Adenylyl Cyclase Activity by a Homogeneous Population of Dopamine Receptors: Selective Blockade by Antisera Directed Against Gi1 and/or Gi2

Sari Izenwasser, Thomas E. Côté

Research output: Contribution to journalArticle

10 Scopus citations

Abstract

The 7315c pituitary tumor cell expresses a homogeneous population of dopamine receptors that are functionally similar to brain dopamine D2 receptors. [3H]-Sulpiride binding to 7315c cell homogenates was specific and saturable, and Ki values for compounds to compete for these sites were highly correlated with values for the same compounds at D2 receptors in brain. Dopamine maximally inhibited ∼65% of forskolin-stimulated cyclase activity in cell membranes. Some D2 agonists had lower efficacies, suggesting that some compounds are partial agonists at this receptor. Removal of GTP from the assay buffer or pretreatment of the tissue with pertussis toxin abolished the inhibition of adenylyl cyclase by dopamine. Immunodetection of most of the known Ga subunits revealed that Gi1, Gi2, Gi3, Go, Gq, and Gs are present in the 7315c membrane. Pretreatment with the AS antibody (which recognizes the C-terminal regions of Gαi1 and Gαi2) significantly attenuated the inhibition of adenylyl cyclase activity by dopamine, whereas antibodies to C-terminal regions of the other Ga subunits had no effect. These findings suggest that the dopamine D2 receptor regulates cyclase inhibition predominantly via Gi1 and/or Gi2 and that the 7315c tumor cells provide a useful model for studying naturally expressed dopamine D2 receptors in the absence of other dopamine receptor subtypes.

Original languageEnglish (US)
Pages (from-to)1614-1621
Number of pages8
JournalJournal of neurochemistry
Volume64
Issue number4
DOIs
StatePublished - Apr 1995
Externally publishedYes

Keywords

  • Cocaine
  • D dopamine receptor
  • Dopamine

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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