, Volume 6, Issue 3, pp 325–333 | Cite as

Dopamine D2 receptor stimulation alters G-protein expression in rat pituitary intermediate lobe melanotropes

  • Scott A. Sands
  • Daniel S. Dickerson
  • Stephen J. Morris
  • Bibie M. Chronwall
Original Articles


Stimulation of dopamine D2 receptors inhibits melanotrope pro-opiomelanocortin (POMC) biosynthesis and α-melanocyte-stimulating hormone (MSH) secretion. These effects are mediated by G-protein αi- and αo- subunits and are reversed by stimulating receptors linked to activation of Gαs protein. Melanotrope activity is increased by haloperidol, a D2 receptor antagonist, and decreased by bromocriptine, a D2 receptor agonist. Both the short and long isoforms of the D2 receptor mRNA and protein increase following chronic haloperidol treatment. After chronic bromocriptine treatment the short isoform is downregulated, whereas the long isoform is upregulated (1). Our hypothesis is that specific G protein α-subunits alter in pattern of expression similarly to the receptor isoforms. Using immunohistochemistry andin situ hybridization, this study examined changes in Gαi'0', and Gαs protein and mRNA expression following chronic treatments with bromocriptine or haloperidol. Gαi3 and Gαo immunoreactivities increased following bromocriptine treatment, whereas Gαs and Gαi1/2 did not change. Gs immunoreactivity increased after haloperidol treatment, whereas Gαi1/2,Gαi3 and Gαo did not change. Gαi and Gαo mRNA increased following bromocriptine and decreased following haloperidol treatments, whereas the inverse results were observed with Gαs mRNA. These results suggest D2 receptor activation can specifically increase Gαi3 and Gαo expression, and D2 receptor blockade increases Gαs expression.

Key Words

Gα-subunits signal transduction receptor regulation in situ hybridization immunohistochemistry 


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Copyright information

© Humana Press Inc 1997

Authors and Affiliations

  • Scott A. Sands
    • 1
  • Daniel S. Dickerson
    • 1
  • Stephen J. Morris
    • 1
  • Bibie M. Chronwall
    • 1
  1. 1.School of Biological SciencesUniversity of Missouri-Kansas CityKansas City

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