VGB-induced reduction of GABA-synthesizing enzyme (GAD-67) abundance, consistent with elevation of GABA levels. Low-power view of immunoreactivity for glutamicacid-decarboxylase isoform GAD-67 in infant rat neocortex, showing the effect of VGB on GAD expression. A, B: From homologous portions of the parietal cortex of a 10-day-old control rat and its VGB-treated littermate, respectively. GAD-67 immunoreactive neurons are seen in all six cortical layers–indicated by roman numerals–of the control section (A). Abundance of GAD-67–immunolabeled cell bodies is substantially reduced after VGB treatment (B). WM, white matter. (Original magnification, ×100).