This is also in agreement with Arendt et al. (1989) showing that in rats treated for 8 weeks with EtOH a full recovery of declined ChAT activity in the basal forebrain is seen after MEK inhibitor 4 weeks of EtOH withdrawal. The effects of EtOH on the cholinergic system may reflect a form of adaptive plasticity, rather than neurodegeneration after EtOH exposure in our brain slice model. In the present study we used EtOH concentrations
from 1 mM (5 mg/dl) up to 100 mM (500 mg/dl). EtOH concentrations between 50 mM (250 mg/dl) to 70 mM (350 mg/dl) are of particular interest, because these levels has been reported in alcohol dependent adults as well as adolescent humans (Deas et al., 2000 and Jones and Holmgren, 2009) and were also used in several in vitro studies (Cheema et al., 2000, Mooney and Miller, 2003 and Zou and Crews, 2010). The sensitivity of the cholinergic system to EtOH has been reported in previous in vivo studies (Arendt et al., 1988, Arendt et al., 1995 and Floyd et al., 1997). In rats prolonged intake of EtOH resulted Talazoparib cell line in a neurotoxic effect on the basal forebrain cholinergic projection system (Floyd et al., 1997) and leads to a partial cholinergic denervation of the cortex, hippocampus and amygdala (Arendt et al., 1988). Beside the cholinergic system, EtOH affects also
other brain areas and EtOH-induced apoptotic cell death in the developing cortex has been observed in organotypic cultures (Mooney and Miller, 2003). In the present study the most prominent decrease of cholinergic neurons of approximately 60% of total neurons was found after treatment with 50 mM (250 mg/dl) EtOH, but not at higher concentrations.
This surprising finding is consistent with data reported by Cheema et al. (2000), who showed that cell death was enhanced in cultures after treatment with 64 mM (320 mg/dl) EtOH but not at 190 mM (950 mg/dl). Others reported Cyclic nucleotide phosphodiesterase that 80 mM (400 mg/dl) EtOH increased cell death in the cortical plate in cultures of rat cerebral cortex, whereas the highest amounts of 160 mM (800 mg/dl) had no effect (Mooney and Miller, 2003). Interestingly, also in human astroglia cells EtOH displayed a biphasic effect: 50 mM EtOH stimulated while 200 mM EtOH inhibited a cytokine-induced iNOS activity (Davis et al., 2002). In our present study we suggest that a saturating effect of < 50 mM EtOH may stimulate a specific single pathway, while at EtOH levels > 50 mM a second, independent and protective pathway may become activated. In the brain, nerve growth factor (NGF) serves as the most potent trophic substance to support survival of cholinergic neurons (Humpel and Weis, 2002 and Levi-Montalcini et al., 1996). In vivo studies showed an increase of NGF mRNA levels in a number of brain areas, including the basal forebrain and their cortical target areas, after chronic EtOH treatment in rats (Arendt et al., 1995).