FIGURE 3.

Influence of GABA_A receptors on migration. (A) Migration defect induced by GABA_A receptor inhibition in vivo. Digital photograph of 50-μm-thick Nissl-stained coronal sections showing a heterotopia (arrow) of a P7 rat treated with a BMI loaded Elvax implant at P0. Scale bars correspond to 200 μm. (B) Schematic drawing illustration the effect of classical and ρ subunit containing GABA_A receptors on radial migration in the developing neocortex. The gray gradient represents the outside directed GABA gradient. In the intermediate zone (IZ) migrating neurons express classical GABA_A and ρ subunit containing GABA_A receptors. In the cortical plate (CP) only classical GABA_A receptors are found. Due to the outside directed GABA gradient the low-affinity classical GABA_A receptors are only activated in the CP, where they contribute to termination of migration (STOP sign). The lower GABA concentration in the IZ is only sufficient to activate the high affinity ρ subunit containing GABA_A receptors, which is necessary to support migration in the IZ (GO sign). Modified from Heck et al. (2007) (A) and Denter et al. (2010) (B).