Binge-like postnatal alcohol exposure triggers cortical gliogenesis in adolescent rats

The long-term effects of binge-like postnatal alcohol exposure on cell proliferation and differentiation in the adolescent rat neocortex were examined. Unlike the hippocampal dentate gyrus, where proliferation of progenitors results primarily in addition of granule cells in adulthood, the vast majority of newly generated cells in the intact mature rodent neocortex appear to be glial cells. The current study examined cytogenesis in the motor cortex of adolescent and adult rats that were exposed to 5.25 g/kg/day of alcohol on postnatal days (PD) 4-9 in a binge manner. Cytogenesis was examined at PD50 (through bromodeoxyuridine [BrdU] labeling) and survival of these newly generated cells was evaluated at PD80. At PD50, significantly more BrdU-positive cells were present in the motor cortex of alcohol-exposed rats than controls. Confocal analysis revealed that the majority (>60%) of these labeled cells also expressed NG2 chondroitin sulfate proteoglycan (NG2 glia). Additionally, survival of these newly generated cortical cells was affected by neonatal alcohol exposure, based on the greater reduction in the number of BrdU-labeled cells from PD50 to PD80 in the alcohol-exposed animals compared to controls. These findings demonstrate that neonatal alcohol exposure triggers an increase in gliogenesis in the adult motor cortex.