Lactobacilli and bifidobacteria ameliorate memory and learning deficits and oxidative stress in β-amyloid (1-42) injected rats

The gastrointestinal microbiota affects brain function, including memory and learning. In this study we investigated the effects of probiotics on memory and oxidative stress biomarkers in an experimental model of Alzheimer's disease. Sixty rats were randomly divided into 5 groups: control; control-probiotics, which received probiotics for 8 weeks; sham operation, which received an intrahippocampal injection of phosphate-buffered saline; Alzheimer, which received an intrahippocampal injection of B-amyloid (A beta 1-42); and Alzheimer-probiotics, which in addition to being injected with A beta 1-42, received 2 g (1 x 10(10) CFU/g) of probiotics (Lactobacillus acidophilus, L fermentum, Bifidobacterium lactis, and B. longum) for 8 weeks. Memory and learning were measured using the Morris water maze, and oxidative stress biomarkers in the hippocampus were measured using ELISA kits. Morris water maze results indicated that compared with the Alzheimer group, the Alzheimer-probiotics group had significantly improved spatial memory, including shorter escape latency and travelled distance and greater time spent in the target quadrant. There was also improvement in oxidative stress biomarkers such as increased malondialdehyde levels and superoxide dismutase activity following the beta-amyloid injection. Overall, it seems that probiotics play a role in improving memory deficit and inhibiting the pathological mechanisms of Alzheimer's disease by modifying microbiota.