Because decreased neurogenesis could be due to effects on any of the components that comprise neurogenesis - proliferation, differentiation, migration or survival - we investigated the components of neurogenesis through the use of BrdU labeling of dividing cells. To examine cell proliferation, the 4D group had BrdU injected 1 h after the last dose of alcohol and rats sacrificed two hours later. Thus, BrdU was examined in adjacent sections. Two alcohol exposed and 1 control did not meet BrdU-labeling criteria (BrdU-labeled mitotic figures were not evident in any region of the brain, (Eisch et al., 2000) and were dropped from this assay. As can be seen in Figure 3, BrdU expression was punctate, with most cells in clusters that were scattered throughout the subgranular zone of both blades of the dentate gyrus as expected. The subgranular zone was defined as a two cell body width between the granule cell layer and hilus. Counting of BrdU-positive (BrdU+) cells revealed a 21.5% decrease (p<0.05) in 4D alcohol-exposed rats (n=4) versus controls (n=5). Therefore, four consecutive days of binge alcohol exposure decreased BrdU-labeling
