Ingestion of Lactobacillus strain reduces anxiety and improves cognitive function in the hyperammonemia rat

Evidence suggests that the hyperammonemia （HA）-induced neuroinflammation and alterations in the serotonin （5-HT） system may contribute to cognitive decline and anxiety disorder during hepatic encephalopathy （HE）. Probiotics that maintain immune system homeostasis and regulate the 5-HT system may be potential treatment for HA-mediated neurological disorders in HE. In this study, we tested the efficacy of probiotic Lactobacillus helveticus strain NS8 in preventing cognitive decline and anxie- ty-like behavior in HA rats. Chronic HA was induced by intraperitoneal injection of ammonium acetate for four weeks in male Sprague-Dawley rats. HA rats were then given Lactobacillus helveticus strain NS8 （109 CFU mL 1） in drinking water as a dai- ly supplementation. The Morris water maze task assessed cognitive function, and the elevated plus maze test evaluated anxie- ty-like behavior. Neuroinflammation was assessed by measuring the inflammatory markers： inducible nitric oxide synthase, prostaglandin E2, and interleukin-1 13 in the brain. 5-HT system activity was evaluated by measuring 5-HT and its metabolite, 5-HIAA, and the 5-HT precursor, tryptophan. Probiotic treatment of HA rats significantly reduced the level of inflammatory markers, decreased 5-HT metabolism, restored cognitive function and improved anxiety-like behavior. These results indicate that probiotic L. helveticus strain NS8 is beneficial for the treatment of cognitive decline and anxiety-like behavior in HA rats.