ABSTRACT.- In a previous study, we reported the in vitro potential probiotic and gamma-aminobutyric acid (GABA) production, of several strains from a collection of Lactiplantibacillus (Lpb) strains within the community of natural whey starters from the artisanal cheese industry. GABA is a non-protein amino acid widely distributed in nature and produced in animals, plants, and microorganisms. However, the best known role of GABA is its function as the major inhibitory neurotransmitter of the central nervous system. Preclinical and clinical evidence suggests that the GABAergic system has a relevant role in mental health disorders, such as anxiety and major depression. The modulation of the GABAergic system has been suggested as a potential strategy for treatment, one such mechanism of modulation is the influence of the microbiota-gut-brain axis through probiotic treatments. The present study was designed to investigate the in vivo probiotic potential of LPB145, a Lactiplantibacillus strain previously characterised as a GABA-producing potentially probiotic strain. Therefore, we evaluated the behavioural effects of chronic oral administration of LPB145 on rats' anxiety- and depression-like behaviours, using the elevated plus maze, open field, and the forced swimming test. The impact of LPB145 strain treatment on the gut microbiota structure and diversity was assessed to discern a possible mechanism of action of the LPB145 treatment through the microbiota-gut-brain axis. Our results showed that LPB145 administration induced an antidepressive-like behaviour without changes in locomotor activity. In contrast, the treatment did not modify the experimental anxiety. The structure and diversity of the intestinal microbiota remained unaffected by the treatment when compared to the control. However, specific clades that could be implicated in the behavioural changes did show differences in their relative abundance. These findings provide evidence regarding the potential of probiotic strains isolated from alimentary sources, to modulate the microbiota-gut-brain axis and positively impact mental health. © J. LOZANO et al., 2024.