title: Cannabinoid CB1 receptor-mediated inhibition of prolactin release and signaling mechanisms in GH4C1 cells.
abstract: The GH4C1 cell line was used to study the cellular mechanisms of cannabinoid-mediated inhibition of PRL release. Cannabinoid CB1 receptor activation inhibited vasoactive intestinal polypeptide- and TRH-stimulated PRL release, but not its basal secretion. The cannabinoid-mediated inhibition of TRH-stimulated PRL release was reversed by the CB1 receptor-specific antagonist, SR141,716A, and was abolished by pertussis toxin pretreatment, indicating that G alpha subunits belonging to the G(i)alpha and G(o)alpha family were involved in the signaling. Photoaffinity labeling using [alpha-32P] azidoaniline GTP showed that cannabinoid receptor stimulation in cell membranes produced activation of four G alpha subunits (G(i)alpha2, G(i)alpha3, G(o)alpha1, and G(o)alpha2), which was also reversed by SR141,716A. The CB1 receptor agonists, WIN55,212-2 and CP55,940, inhibited cAMP formation and calcium currents in GH4C1 cells. The subtypes of calcium currents inhibited by WIN55,212-2 were characterized using holding potential sensitivity and calcium channel blockers. WIN55,212-2 inhibited the omega-conotoxin GVIA (Conus geographus)- and omega-agatoxin IVA (Aigelenopsis aperta)-sensitive calcium currents, but not the nisoldipine-sensitive calcium currents, suggesting the inhibition of N- and P-type, but not L-type, calcium currents. Taken together, the present findings indicate that CB1 receptors can couple through pertussis toxin-sensitive G alpha subunits to inhibit adenylyl cyclase and calcium currents and suppress PRL release from GH4C1 cells.
authors.affiliation: Department of Pharmacology and Toxicology, University of North Dakota, Grand Forks 58203-2817, USA. bho@badlands.nodak.edu
authors.forename: B Y
authors.initials: BY
authors.lastname: Ho
authors.forename: A
authors.initials: A
authors.lastname: Stadnicka
authors.forename: P L
authors.initials: PL
authors.lastname: Prather
authors.forename: A R
authors.initials: AR
authors.lastname: Buckley
authors.forename: L L
authors.initials: LL
authors.lastname: Current
authors.forename: Z J
authors.initials: ZJ
authors.lastname: Bosnjak
authors.forename: W M
authors.initials: WM
authors.lastname: Kwok
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D048588:Benzoxazines; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D002186:Cannabinoids / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D015737:Nisoldipine / Q000494:pharmacology; D019920:Photoaffinity Labels; D010911:Pituitary Neoplasms / Q000378:metabolism; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000378:metabolism*; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D048588:Benzoxazines; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002186:Cannabinoids; D009025:Morpholines; D009281:Naphthalenes; D019920:Photoaffinity Labels; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; D015737:Nisoldipine; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; D011388:Prolactin; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases