Figure 8.

mGlu7-mediated axon outgrowth is regulated by the MAPK-cAMP pathway, but is independent of the G_αi pathway. A, Cortical neurons (DIV1) were cotransfected with EGFP and the control vector (Vec), mGlu7 I154T or R658W/T675K rescue constructs in the absence or presence of rolipram (500 nm). At DIV3, axonal outgrowth was visualized by confocal microscopy and measured by NeuronJ software. Scale bar: 50 μm. Scatter plots represent the mean ± SEM, n.s., not significant, *p < 0.0001. B, mGlu7-mediated axon outgrowth is not related to the G_αi signaling pathway. After cortical neurons (DIV1) were transfected with EGFP, the neurons were treated with AMN082 in the presence or absence of 2, 4, or 10 μg/ml PTX, an inhibitor of G_α subunits of the heterotrimeric G-protein. At DIV3, axonal outgrowth was visualized by confocal microscopy. Scale bar: 50 μm. Scatter plots represent the mean ± SEM. *p < 0.0001, **p = 0.0041, ***p = 0.0085. C, MAPK is an upstream mediator of cAMP in mGlu7-mediated axon outgrowth. After transfection with EGFP, the cortical neurons (DIV1) were treated with MEK inhibitor (PD98059) and/or 500 nm rolipram, a PDE inhibitor that suppresses cAMP degradation, in the absence or presence of the mGlu7 agonist AMN082. At DIV3, axonal outgrowth was visualized by confocal microscopy. Scale bar: 50 μm. Scatter plots represent the mean ± SEM, n.s., not significant, *p < 0.0001.