Age-related effects of moderate alcohol consumption on GAP-43 levels in rat hippocampus

The effects of moderate intake of ethanol and ageing were investigated on t he levels of the growth-associated protein GAP-43, whose expression has bee n used as an indicator of axonal growth during development, regeneration an d remodelling of synaptic connections. Groups of fi-male Wistar rats (12 an d 24 months of age), were alcohol-fed for one month while age-matched contr ol groups received an isocaloric diet. A quantitative evaluation of GAP-43 was performed in hippocampus and in hippocampal selected areas in view of t he vulnerability of this complex to alcohol aggression by means of two diff erent methods, namely Western blot analysis and immunohistochemistry. While the former measures total extractable GAP-43, the latter allows visualisat ion of in situ changes in topographical distribution of GAP-43. Western blo t analysis revealed an age-dependent reduction (-47%) and an ethanol-associ ated increase (81%) of GAP-43 demonstrated only in the old group. Conversel y, quantitative immunohistochemistry of GAP-43 in the entire hippocampus sh owed a, non-significant ethanol-related decrement in 24-month-old rats (-30 %), although the age-dependent reduction was confirmed. Ageing was associat ed with a decrement of GAP-43 immunostaining in CA3 stratum radiatum (CA3) and in inner molecular layer of dentate gyrus (IML). Treatment determined a decrease of GAP-43 immunostaining in adult rat CA3 and IML and no change i n CAI stratum radiatum (CAI). Our results suggest that immunohistochemistry evaluation underestimates GAP-43 levels in ethanol-treated animals possibl y as a consequence of conformational changes induced by alcohol, resulting in non-targeting of the specific antibody. Western blot analysis demonstrat e that although there is a reduction of GAP-43 levels in hippocampus of age d rats, this structure retain a remarkable potential to compensate for etha nol toxicity during ageing. (C) 2001 Elsevier Science Ireland Ltd. All righ ts reserved.