Antibiotics Disrupt Development of the ‘Social Brain’ in Mice

Summary: Early-life exposure to antibiotics may impact brain signaling pathways associated with social behavior and pain regulation. Young mice treated with antibiotics had reduced expression of receptors that mediate endorphin, oxytocin, and vasopressin signaling in the frontal cortex.

Source: University of Oxford

Antibiotic treatment in early life seems to impede brain signalling pathways that function in social behaviour and pain regulation in mice, a new study by Dr Katerina Johnson and Dr Philip Burnet has found. It was published today in BMC Neuroscience.

Katerina Johnson, from the University’s Departments of Psychiatry and Experimental Psychology, was researching the effects of disrupting the microbiome on the brain in mice. ‘We know from previous research that animals missing microbes, such as germ-free animals (which are devoid of microbes) or antibiotic-treated animals (whose microbes are severely depleted), have impaired social behaviour,’ she explains. ‘I was therefore particularly interested in the effects of the microbiome on endorphin, oxytocin and vasopressin signalling since these neuropeptides play an important role in social and emotional behaviour.’

The most striking finding was in young animals treated with antibiotics. This resulted in reduced expression of the receptors which mediate endorphin, oxytocin and vasopressin signalling in the frontal cortex. Dr Johnson commented, ‘If these signalling pathways are less active, this may help explain the behavioural deficits seen in antibiotic-treated animals. Whilst this study was in animals given a potent antibiotic cocktail, this finding highlights the potential detrimental effects that antibiotic exposure may have on the brain when it’s still developing.’

Dr Burnet added, ‘Our research underlines the growing consensus that disturbing the microbiome during development can have significant impacts on physiology, including the brain.’

The study was conducted using a relatively small number of animals with high doses of antibiotics and further research should follow up this finding given society’s reliance on antibiotics, though of course they still play a vital role in medicine to fight bacterial infections.

This shows antibiotic pills
This resulted in reduced expression of the receptors which mediate endorphin, oxytocin and vasopressin signalling in the frontal cortex. Image is in the public domain.

This was also the first study to investigate whether the microbiome affects the brain’s endorphin system (where endorphin activates opioid receptors) and so these findings may have clinical relevance. Dr Johnson said, ‘The adverse effect of antibiotics on the endorphin system may have implications not only for social behaviour but also for pain regulation. In fact we know that the gut microbiome affects the pain response so this might be one of the ways in which it does so.’

‘A somewhat surprising observation from our research was the contrast in results for germ-free and antibiotic-treated mice, since the neurogenetic changes were generally in the opposite direction. This is a pertinent finding as the use of antibiotics to deplete the microbiome is often seen as a more accessible alternative to germ-free animals. However, we highlight the need to consider these two treatments as distinct models of microbiome manipulation when investigating the effects of microbes on the brain and behaviour.’

Thanks to Dr. Katerina Johnson for submitting this article to Neuroscience News. Follow Dr. Johnson on Twitter via @DrKatJohnson.

About this neurodevelopment research article

Oxford University
Media Contacts:
Katerina Johnson – University of Oxford
Image Source:
The image is in the public domain.

Original Research: Open access
“Opposing effects of antibiotics and germ-free status on neuropeptide systems involved in social behaviour and pain regulation”. by Katerina V. A. Johnson & Philip W. J. Burnet. BMC Neuroscience.


Opposing effects of antibiotics and germ-free status on neuropeptide systems involved in social behaviour and pain regulation

Recent research has revealed that the community of microorganisms inhabiting the gut affects brain development, function and behaviour. In particular, disruption of the gut microbiome during critical developmental windows can have lasting effects on host physiology. Both antibiotic exposure and germ-free conditions impact the central nervous system and can alter multiple aspects of behaviour. Social impairments are typically displayed by antibiotic-treated and germ-free animals, yet there is a lack of understanding of the underlying neurobiological changes. Since the μ-opioid, oxytocin and vasopressin systems are key modulators of mammalian social behaviour, here we investigate the effect of experimentally manipulating the gut microbiome on the expression of these pathways.

We show that social neuropeptide signalling is disrupted in germ-free and antibiotic-treated mice, which may contribute to the behavioural deficits observed in these animal models. The most notable finding is the reduction in neuroreceptor gene expression in the frontal cortex of mice administered an antibiotic cocktail post-weaning. Additionally, the changes observed in germ-free mice were generally in the opposite direction to the antibiotic-treated mice.

Antibiotic treatment when young can impact brain signalling pathways underpinning social behaviour and pain regulation. Since antibiotic administration is common in childhood and adolescence, our findings highlight the potential adverse effects that antibiotic exposure during these key neurodevelopmental periods may have on the human brain, including the possible increased risk of neuropsychiatric conditions later in life. In addition, since antibiotics are often considered a more amenable alternative to germ-free conditions, our contrasting results for these two treatments suggest that they should be viewed as distinct models.

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