Differential susceptibility following β-amyloid peptide-(1–40) administration in C57BL/6 and Swiss albino mice: Evidence for a dissociation between cognitive deficits and the glutathione system response

Considerable evidence supports the role of oxidative stress in the pathogenesis of Alzheimer's disease (AD). Previous studies suggest that the central nervous system (CNS) administration of β-amyloid peptide, the major constituent of senile plaque in AD, induces oxidative stress in rodents which may contribute to the learning and memory deficits verified in the β-amyloid model of AD. In the present study, we compared the effects of a single intracerebroventricular (i.c.v.) injection of aggregated β-amyloid peptide-(1–40) (Aβ1–40) (400 pmol/mouse) on spatial learning and memory performance, synaptic density and the glutathione (GSH)-dependent antioxidant status in adult male C57BL/6 and Swiss albino mice. Seven days after Aβ1–40 administration, C57BL/6 and Swiss mice presented similar spatial learning and memory impairments, as evaluated in the water maze task, although these impairments were not found in Aβ40–1-treated mice. Moreover, a similar decline of synaptophysin levels was observed in the hippocampus (HC) and prefrontal cortex (PFC) of both Swiss and C57BL/6 mice treated with Aβ1–40, which suggests synaptic loss. C57BL/6 mice presented lower levels of glutathione-related antioxidant defences (total glutathione (GSH-t) levels, glutathione peroxidase (GPx) and glutathione reductase (GR) activity) in the HC and PFC in comparison to Swiss mice. Despite the reduced basal GSH-dependent antioxidant defences observed in C57BL/6 mice, Aβ1–40 administration induced significant alterations in the brain antioxidant parameters only in Swiss mice, decreasing GSH-t levels and increasing GPx and GR activity in the HC and PFC 24 h after treatment. These results indicate strain differences in the susceptibility to Aβ1–40-induced changes in the GSH-dependent antioxidant defences in mice, which should be taken into account in further studies using the Aβ model of AD in mice. In addition, the present findings suggest that the spatial learning and memory deficits induced by β-amyloid peptides in rodents may not be entirely related to glutathione-dependent antioxidant response.