Interaction of D₃ preferring agonist (-)-N ⁶-(2-(4- (biphenyl-4-yl)piperazin-1-yl)ethyl)-N ⁶-propyl-4,5,6,7- tetrahydrobenzo[d]thiazole-2,6-diamine (D-264) with cloned human D_2L, D_2S, and D₃ receptors: Potent stimulation of mitogen-activated protein kinases and G protein-coupled inward rectifier potassium channels

This study aims to determine the effect of the novel D₃ dopamine receptor agonist, D-264, on activation of D₃ and D₂ dopamine receptor signal transduction pathways and cell proliferation. AtT-20 neuroendocrine cells stably expressing human D_2S, D_2L, and D₃ dopamine receptors were treated with D-264 and the coupling of the receptors to mitogen-activated protein kinase (MAPK) and G protein-coupled inward rectifier potassium (GIRK) channels was determined using Western blotting and whole-cell voltage clamp recording, respectively. D-264 potently activated MAPK signaling pathway coupled to D_2S, D_2L, and D ₃ dopamine receptors. The activation of MAPK was more pronounced than the reference agonist quinpirole and was longer lasting. D-264 also activated GIRK channels coupled to D_2S, D_2L, and D₃ receptors. In addition, D-264 dose-dependently induced cell proliferation in AtT-D_2L and AtT-D₃ cells. These results indicate that D-264 robustly activates GIRK channels and MAPK coupled to D₂ and D₃ dopamine receptors in AtT-20 cells. D-264 is also a potent inducer of cell proliferation.