aspects of the cell cycle: Ki-67 is expressed during all active phases of the cell cycle (M G2, S and G1; Scholzen and Gerdes, 2000) whereas BrdU is incorporated into cells when the DNA is singled stranded, during the S-phase. Comparison of the Ki67 and BrdU data suggests that alcohol may arrest cells in the G1 phase. Arresting cells in G1 or increasing the length of the cell cycle would result in decreased numbers of BrdU+ cells (S-phase) and similar numbers of Ki-67+ cells (all active phases) similar to the pattern observed. Alcohol- induced effects on cell proliferation by increasing the length of G1 or inhibiting the progression of cells from G1 to S-phase of the cell cycle has long been suggested as an effect of alcohol on fetal brain development (Jacobs, 2001; Luo and Miller, 1998; Miller and Nowakowski, 1991). Further, other drugs of abuse impact adult neurogenesis via cell cycle alterations (Mandyam et al., 2008).
