Cannabinoid CB1 Receptor-Mediated Inhibition of Prolactin Release and Signaling Mechanisms in GH4C1 Cells

Endocrinology. 2000 May;141(5):1675-85. doi: 10.1210/endo.141.5.7454.

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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenylyl Cyclases / metabolism
  • Animals
  • Benzoxazines
  • Calcium Channel Blockers / pharmacology
  • Calcium Channels / metabolism
  • Cannabinoids / metabolism*
  • GTP-Binding Proteins / metabolism
  • Morpholines / pharmacology
  • Naphthalenes / pharmacology
  • Nisoldipine / pharmacology
  • Photoaffinity Labels
  • Pituitary Neoplasms / metabolism
  • Prolactin / metabolism*
  • Rats
  • Receptors, Cannabinoid
  • Receptors, Drug / metabolism*
  • Signal Transduction*
  • Tumor Cells, Cultured
  • Type C Phospholipases / metabolism

Substances

  • Benzoxazines
  • Calcium Channel Blockers
  • Calcium Channels
  • Cannabinoids
  • Morpholines
  • Naphthalenes
  • Photoaffinity Labels
  • Receptors, Cannabinoid
  • Receptors, Drug
  • Nisoldipine
  • Win 55212-2
  • Prolactin
  • Type C Phospholipases
  • GTP-Binding Proteins
  • Adenylyl Cyclases