Abstract <p>Previous studies have shown that two rat strains selectedby the excitability threshold of the nervous system exhibit differencesin response to prolonged emotional-pain stress at behavioral, neurobiological, andmolecular genetic levels, as well as specific changes in gut microbiotacomposition, suggesting a potential link between genetic factors,microbiota, and behavioral disorders. The aim of this study is to analyzethe gut microbiota and behavioral profiles in intact rats with high(HT) and low (LT) excitability thresholds to identify key differencesdriven by their genetic characteristics. The behavior of intactrats from two strains was analyzed in the Open Field and ElevatedPlus Maze, and microbiota analysis in stool samples was conductedusing 16S rRNA gene amplicon sequencing. Behavioral analysis revealed thathigh-excitability (LT) rats exhibited higher activity and reducedfreezing in the Elevated Plus Maze compared to low-excitability(HT) rats. While alpha diversity indices of gut microbiota showedno significant inter-strain differences, beta diversity analysisrevealed significant differences in microbial profiles between HTand LT rats. LT rats had a significantly higher abundance of <i>Lactobacillus</i> and <i>Faecalibacterium</i> genera comparedto HT animals, whereas HT rats demonstrated a higher relative abundanceof <i>Romboutsia</i>, <i>Eubacterium</i>, and <i>Turicibacter</i> genera. Thus, the dataof behavioral and microbiota analyses highlight a potential linkbetween genetic factors, gut microbiota profiles, and the uniquephysiological and behavioral traits of rat strains selected forthe excitability threshold of the nervous system.</p>