Loss of TH+ neurons and fibers in the VM of Top IIβ null mice. TH-immunostaining was performed in sagittal sections of E18.5 Top IIβ+/+ and Top IIβ-/- mice brains. The location of TH+ neurons areas were indicated by horizontal arrows (SNc) and arrowheads (VTA). Vertical arrowheads indicated the location of the TH+ fibers extended from SNc and VTA (a and b). c and d showed in higher magnification that the TH+ neurons in SNc was loss in Top IIβ-/- mice, while the number also decreased in VTA. Bar = 100 μm.