Effects of antibiotics and galacto-oligosaccharide on behaviors and neurotransmitters in rats

Abstract:

Galacto-oligosaccharides (GOS) as prebiotics can regulate gut microbiota to improve brain development, whereas antibiotics can affect the nervous system by interfering with gut microbiota. The mechanisms of antibiotics and GOS in regulating brain neurotransmitters and animal behaviors remain unknown.Objective To investigate the effects of antibiotics and GOS on the behaviors and neurotransmitters in weaned Sprague-Dawley (SD) rats.Methods Forty 3-week-old male SD rats were selected and assigned into four groups: control (CON, sterilized water), antibiotics (ABX), GOS (5 g/L), and antibiotics+GOS (AG). The antibiotics used in the experiment were composed of ampicillin, vancomycin, ciprofloxacin hydrochloride, imipenem, and metronidazole. The experiment lasted for 16 days.Results The body weight of rats in the ABX group was lower than that in the GOS group (P<0.05), and the liver index in the ABX, GOS, and AG groups was lower than that in the CON group (P<0.05). Compared with the CON group, the ABX group showcased decreased phototaxis index (percentage of time in bright during bright-dark box test) and reduced times of self-grooming (P<0.05), and the GOS group had reduced times of self-grooming (P<0.05). The AG group had longer resting time in the open field than the other three groups (P<0.05) and shorter distance, shorter time, and slower movement than ABX and GOS groups (P<0.05). Compared with the CON group, the ABX group showcased elevated level of norepinephrine and lowered level of levodopa in the hippocampus (P<0.05). Compared with the CON group, the GOS and AG groups demonstrated elevated levels of norepinephrine and declined levels of levodopa and epinephrine (P<0.05). Compared with the CON group, the ABX and AG groups presented decreased microbial diversity (P<0.05), where Escherichia_Shigella became dominant. The Chao1 index in the GOS group was lower than that in the CON group (P<0.05). The dominant bacteria in the GOS group were Firmicutes and Bacteroidota. Compared with that in the ABX group, the relative abundance of Lactobacillus increased in the AG group (P<0.05).Conclusion ABX decreased anxiety-like behaviors compared with CON, while reducing levodopa and increasing norepinephrine in the hippocampus and enriching potentially pathogenic bacteria. GOS improved growth without influencing the behaviors of rats, and meanwhile it increased the relative abundance of Lactobacillus and decreased levodopamine and norepinephrine in the hippocampus. The combined use of ABX and GOS decreased the locomotor activity and increased the anxiety-like behaviors of rats.

Key words:antibiotics;galacto-oligosaccharides (GOS);gut microbiota;social behavior;neurotransmitters