Apoptotic cell death and temporal expression of apoptotic proteins Bcl-2 and Bax in the hippocampus, following binge ethanol in the neonatal rat model.

BACKGROUND

Binge-like ethanol (EtOH) exposure during the early rat neonatal period results in acute cell loss in specific brain regions, but such acute cell death has not been well established in the hippocampus. Binge alcohol exposure can also result in protein expression changes in the cerebellum that could alter cell fate, but this has not been reported for the hippocampal subregions. This study investigates acute apoptotic cell death in hippocampal regions CA1, CA3, and dentate gyrus (DG) following a binge EtOH exposure on postnatal day (PN) 6, PN8, or PN6 + 8 and the alteration in pro- and anti-apoptotic proteins following a single EtOH binge on PN6.

METHODS

Apoptotic cell death was quantified 12 hours after EtOH binge exposure using the optical fractionator method. Western blot analysis determined expression of pro-apoptotic Bax and anti-apoptotic Bcl-2, 12, 24, and 48 hours after binge EtOH exposure on PN6. The Bcl-2:Bax ratio was used as a measure of vulnerability to apoptosis.

RESULTS

Acute apoptosis increased significantly 12 hours following PN6 or 8 EtOH exposure in CA1, CA3, and DG, but the magnitude of apoptotic cell death was significantly greater in CA1 than in CA3 and DG, which did not differ. Significant cell death was not detected when a PN8 EtOH exposure was preceded by exposure on PN6. Binge EtOH exposure on PN6 resulted in a significant increase in expression of Bcl-2 and the Bcl-2:Bax ratio in the CA1/DG region at 24 hours after EtOH exposure on PN6. The Bcl-2:Bax ratio in the CA3 region was not altered.

CONCLUSIONS

This study shows that repeated binge exposure does not have a cumulative effect on the magnitude of acute apoptotic cell death. This finding may be explained in part by changes in the Bcl-2:Bax ratio after a single binge EtOH exposure.