Do Overall Activity Levels Influence the Orientation of Migrating Cells?
Many of our findings suggest that overall activity levels are altered in MAM-treated cortex. This notion is strengthened by the altered distribution of interneurons in juvenile ferrets (Figs 5 and 6) and previous findings of changes in GABAA receptor distribution and cortical response profiles (Jablonska et al. 2004; McLaughlin and Juliano 2005). In the embryonic mouse, cells migrating tangentially express GABAA receptors (Soria and Valdeomillos 2002). To assess if tangentially migrating cells also express GABAA receptors in ferrets, we labeled migrating cells by placing crystals of DiI into the GE of normal slices. After 5 DIC, the slices were fixed and immunoreacted against the chain of the GABAA receptor. DiI-positive cells leaving the GE clearly express GABAA receptors (Supplementary Fig. 5). To determine if altering overall activity levels in normal cortex mimicked the impairment in orientation seen in MAM-treated cortex, we exposed normal cortical organotypic slices to BIC (10 µM
