Long-term administration of yoghurt improves spatial memory in mice

Abstract

Gut microbiota modulate host behavior by altering their brain function through vagal nerve stimulation, the immune system, or the release of hormones. We recently reported that the gut microbiota modifies free amino acid concentrations in the brain. Although many studies of functional lactobacillus have been reported, the role of lactobacillus in learning ability has not been clarified. Cognitive dysfunction syndrome with aging causes abnormal behavior and memory disorders in many animals, including humans,dogs or cats. We investigated the effect of long-term administration of yoghurt （fermented by Lactobacillus delbrueckii subsp. bulgaricus 2038 and Streptococcus thermophilus 1131） on the spatial memory and amino acid and monoamine concentrations in the cerebral cortex of mice. Long-term administration of yoghurt improved the test scores for spatial reference memory on the eight-arm radial maze and increased 5-hydroxytryptamine,and the cerebral cortex concentrations of free L-alanine, D- and L-serine, L-valine, and L-isoleucine. These results suggest that the long-term intake of yoghurt by mice might improve the spatial reference memory through modification of the metabolism of several amino acids and 5-hydroxytryptamine in the cerebral cortex.