Lead-induced effects on learning/memory and fear/anxiety are correlated with disturbances in specific cholinesterase isoform activity and redox imbalance in adult brain

- Pb caused significant deficits on mice learning/memory ability and increased anxiety.
- Pb inhibited the AChE G4 and G1 activities in all brain regions tested.
- Pb increased lipid peroxidation and decreased GSH levels in all brain regions.
- Coefficients between behavior, AChE activity and redox balance were brain region-specific.

The aim of the present study was to investigate whether the underlying mechanism of lead (Pb)-induced effects on learning/memory and fear/anxiety behavior involves changes either on AChE G4 (most abundant in brain) or on G1 isoform activity, and/or to a putative local disruption of oxidant/antioxidant balance. Adult male mice were randomly divided into two groups (18 animals/group): a vehicle group [500 ppm (mg/L) CH3COONa/day for 4 weeks in their drinking water] and a Pb-treated group [500 ppm Pb(CH3COO)2/day for 4 weeks in their drinking water]. At the end of the treatment period, mice were subjected to the behavioral tasks. Learning/memory was tested by step-through passive avoidance test, whereas fear/anxiety was studied using the elevated plus-maze and thigmotaxis tests. Pb levels in mice brain were determined using atomic absorption spectrometry. AChE activity was determined colorimetrically, and GSH and MDA levels fluorometrically in whole brain minus cerebellum, cerebral cortex, midbrain, hippocampus, striatum and cerebellum. The possible correlations between learning/memory or fear/anxiety behavior with the AChE activity and/or the lipid peroxidation levels and GSH content were also examined. Pb consumption caused significant deficits on mice learning/memory ability and increased anxiety. The consumption of the Pb solution inhibited the activity of the two AChE isoforms in all brain regions tested. Moreover, Pb exposure increased lipid peroxidation and decreased GSH levels in all brain regions examined. Spearman correlation analysis revealed that the coefficients between the particular behaviors, AChE activity and redox balance were brain region- and AChE isoform-specific.