Fig. 4. Level of tyrosine hydroxylase (Th) protein measured by immunohistochemistry in wild-type and ak brain sections. (A) Coronal section of the mesencephalic dopaminergic (mesDA) neuronal region. The normal architecture of the system is indicated in the wild-type (arrows). Similar sections from the ak brain are paired to match the wild-type level. (B) The left two panels indicate the neurons of the mesDA system and their architecture, the projecting axons and the target area in the striatum in sagittal sections. The right two panels show similar sections in the ak brain with the altered mesDA neuron architecture and the missing projection area in the caudate putamen indicated by the asterisk. (C) Th expression in coronal sections of the striatal area. CPu, caudate putamen; MFB, main forebrain bundle; VTA, ventral tegmental area; SNc, substantia nigra compacta; Acb, nucleus accumbens; Tu, tubercle olfactorium.