This study aimed to comprehensively evaluate the influence of the probiotic strain Bacillus subtilis on behavioral responses and serum biochemical parameters in mice under conditions of lipopolysaccharide (LPS)-induced systemic inflammation. The experimental model using C57BL/6 mice demonstrated the probiotic's pronounced modulating effect on key behavioral aspects. The administration of B. subtilis significantly reduced the frequency of grooming acts, which is interpreted as a reduction in anxiety and a manifestation of an anxiolytic effect. Simultaneously, an increase in exploratory activity was observed, manifested by a rise in the number of hole pokes and vertical rearings in the Open Field test, indicating a potential positive impact on cognitive functions. In contrast, LPS-induced inflammation caused suppression of exploratory activity and a decrease in defecation, reflecting a negative impact on intestinal peristalsis and the general stress state of the animals. Biochemical analysis revealed a duality of B. subtilis effects: alongside behavioral improvement, a statistically significant increase in serum urea levels was recorded, which may be indirectly related to microbiome restructuring and metabolic shifts. Concurrently, a decrease in cholesterol concentration was detected in the LPS group, likely due to macrophage activation and disruption of its synthesis. The obtained data emphasize the complex nature of the interaction between the probiotic and host physiology, indicating the need for further study of the mechanisms of B. subtilis influence on the gut-brain axis and metabolism under inflammatory conditions to develop effective strategies for correcting LPS-induced disorders.

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