Differential G protein-mediated coupling of D 2 dopamine receptors to K + and Ca 2+ currents in rat anterior pituitary cells

Abstract

In anterior pituitary cells, dopamine, acting on D 2 dopamine receptors, concomitantly reduces calcium currents and increases potassium currents. These dopamine effects require the presence of intracellular GTP and are blocked by pretreatment of the cells with pertussis toxin, suggesting that one or more G protein is involved. To identify the G proteins involved in coupling D 2 receptors to these currents, we performed patch-clamp recordings in the whole-cell configuration using pipettes containing affinity-purified polyclonal antibodies raised against either G oα, G 3α, or G i1,2α. Dialysis with G oα antiserum significantly reduced the inhibition of calcium currents induced by dopamine, while increase of potassium currents was markedly attenuated only by G i3α antiserum. We therefore conclude that in pituitary cells, two different G proteins are involved in the signal transduction mechanism that links D 2 receptor activation to a specific modulation of the four types of ionic channels studied here.