Many factors influence human emotions and behavior. A key player in their regulation is the gut microbiome – the community of microbes that resides in the intestinal tract. Findings from a new study show indicate that antibiotic use early in life alters neuropeptide signaling pathways that influence behavioral development.

Antibiotics are often prescribed to treat ear infections, respiratory illness, and diarrhea in children. They are among the most commonly prescribed drugs among children living in the United States.

Neuropeptide signaling pathways are the means by which neurons communicate with each other. Three primary pathways modulate human behavior, namely the opioid, oxytocin, and vasopressin systems. The opioid system modulates social behavior, mediates physical pain, and participates in social attachment and other aspects of behavior and emotion. Oxytocin and vasopressin play roles in social cognition, pair bonding, and sexual behaviors.

The authors of the mouse study allocated the animals to one of two groups to receive either drinking water containing a cocktail of antibiotics or drinking water alone for three weeks. The antibiotic cocktail contained ampicillin, vancomycin, neomycin, metronidazole, and amphotericin-B – a mixture that is known to eradicate the gut bacteria without killing the mice.

The mice that received the antibiotics demonstrated altered neuropeptide gene expression in the frontal cortex and brain stem regions, which might explain the altered behavior observed in mice that received the same cocktail in other experiments. These findings demonstrate that antibiotic use in early life may alter behavior and underscores the importance of efforts to reduce the overprescribing of antibiotics.

• Link to full study.