Dopamine D3 receptor activation promotes neural stem/progenitor cell proliferation through AKT and ERK1/2 pathways and expands type-B and -C cells in adult subventricular zone

The neurotransmitter dopamine acts on the subventricular zone (SVZ) to regulate both prenatal and postnatal neurogenesis, in particular through D3 receptor (D3R) subtype. In this study, we explored the cellular mechanism(s) underlying D3R-mediated cell proliferation and tested if systemic delivery of a D3R agonist would induce SVZ multipotent neural stem/precursor cell (NSC/NPC) proliferation in vivo. We found that treatment with the D3R agonist, 7-OH-DPAT, enhances cell proliferation in a dose-dependent manner in cultured SVZ neurospheres from wild-type, but not D3R knock-out mice. Furthermore, D3R activation also stimulates S-phase and enhances mRNA and protein levels of cyclin D1 in wild-type neurospheres, a process which requires cellular Akt and ERK1/2 signaling. Moreover, chronic treatment with low dose 7-OH-DAPT in vivo increases BrdU+ cell numbers in the adult SVZ, but this effect was not seen in D3R KO mice. Additionally, we probed the cell type specificity of D3R agonist-mediated cell proliferation. We found that in adult SVZ, GFAP+ astrocytes, type-B GFAP+/nestin+ and type-C EGF receptor (EGFR+)/nestin+ cells express D3R mRNA, but type-A Doublecortin (Dcx)+ neuroblasts do not. Using flow cytometry and immunofluorescence, we demonstrated that D3R activation increases GFAP+ type-B and EGFR+ type-C cell numbers, and the newly divided Dcx+ type-A cells. However, BrdU+/Dcx+ cell numbers were decreased in D3R KO mice compared to wildtype, suggesting that D3R maintains constitutive NSC/NPCs population in the adult SVZ. Overall, we demonstrate that D3R activation induces NSC/NPC proliferation through Akt and ERK1/2 signaling and increases the numbers of type-B and -C NSC/NPCs in the adult SVZ. © 2013 Wiley Periodicals, Inc.