PTX-sensitive regulation of neurite outgrowth by the dopamine D₃ receptor

Neurotransmitter receptors are known to have direct roles in the modulation of neuronal morphogenesis. Previous work showed that clonal mesencephalic MN9D cells individually transfected with D₂-like dopamine receptors show increased neurite outgrowth following long-term exposure to the D₂-like receptor agonist quinpirole. In the current study, brief stimulation of D₃ receptor-expressing cells also elicited increased neurite outgrowth, which could be mimicked by the G(i)/G(o) protein activator mastoparan. Pretreatment with the G(i)/G(o) protein inhibitor pertussis-toxin blocked the quinpirole- and mastoparan-mediated increases in outgrowth. These results suggest that dopamine D₃ receptor stimulation has an immediate, G-protein-mediated role in neuronal morphogenesis.