Psychotropic effects of Lactobacillus plantarum PS128 in early life-stressed and naive adult mice

Ingestion of specific probiotics, namely psychobiotics, produces psychotropic effects on behavior and affects the hypothalamic-pituitary-adrenal axis and neurochemicals in the brain. We examined the psychotropic effects of a potential psychobiotic bacterium, Lactobacillus plantarum strain PS128 (PS128), on mice subjected to early life stress (ELS) and on naive adult mice. Behavioral tests revealed that chronic ingestion of PS128 increased the locomotor activities in both ELS and naive adult mice in the open field test. In the elevated plus maze, PS128 significantly reduced the anxiety-like behaviors in naive adult mice but not in the ELS mice; whereas the depression-like behaviors were reduced in ELS mice but not in naive mice in forced swimming test and sucrose preference test. PS128 administration also reduced ELS-induced elevation of serum corticosterone under both basal and stressed states but had no effect on naive mice. In addition, PS128 reduced inflammatory cytokine levels and increased anti-inflammatory cytokine level in the serum of ELS mice. Furthermore, the dopamine level in the prefrontal cortex (PFC) was significantly increased in PS128 treated ELS and naive adult mice whereas serotonin (5 HT) level was increased only in the naive adult mice. These results suggest that chronic ingestion of PS128 could ameliorate anxiety-and depression-like behaviors and modulate neurochemicals related to affective disorders. Thus PS128 shows psychotropic properties and has great potential for improving stress-related symptoms. (C) 2015 The Authors. Published by Elsevier B.V.