Gastroenterology

Gastroenterology

Volume 141, Issue 2, August 2011, Pages 599-609.e3
Gastroenterology

Original Research
Basic and Translational—Alimentary Tract
The Intestinal Microbiota Affect Central Levels of Brain-Derived Neurotropic Factor and Behavior in Mice

https://doi.org/10.1053/j.gastro.2011.04.052Get rights and content

Background & Aims

Alterations in the microbial composition of the gastrointestinal tract (dysbiosis) are believed to contribute to inflammatory and functional bowel disorders and psychiatric comorbidities. We examined whether the intestinal microbiota affects behavior and brain biochemistry in mice.

Methods

Specific pathogen–free (SPF) BALB/c mice, with or without subdiaphragmatic vagotomy or chemical sympathectomy, or germ-free BALB/c mice received a mixture of nonabsorbable antimicrobials (neomycin, bacitracin, and pimaricin) in their drinking water for 7 days. Germ-free BALB/c and NIH Swiss mice were colonized with microbiota from SPF NIH Swiss or BALB/c mice. Behavior was evaluated using step-down and light preference tests. Gastrointestinal microbiota were assessed using denaturing gradient gel electrophoresis and sequencing. Gut samples were analyzed by histologic, myeloperoxidase, and cytokine analyses; levels of serotonin, noradrenaline, dopamine, and brain-derived neurotropic factor (BDNF) were assessed by enzyme-linked immunosorbent assay.

Results

Administration of oral antimicrobials to SPF mice transiently altered the composition of the microbiota and increased exploratory behavior and hippocampal expression of BDNF. These changes were independent of inflammatory activity, changes in levels of gastrointestinal neurotransmitters, and vagal or sympathetic integrity. Intraperitoneal administration of antimicrobials to SPF mice or oral administration to germ-free mice did not affect behavior. Colonization of germ-free BALB/c mice with microbiota from NIH Swiss mice increased exploratory behavior and hippocampal levels of BDNF, whereas colonization of germ-free NIH Swiss mice with BALB/c microbiota reduced exploratory behavior.

Conclusions

The intestinal microbiota influences brain chemistry and behavior independently of the autonomic nervous system, gastrointestinal-specific neurotransmitters, or inflammation. Intestinal dysbiosis might contribute to psychiatric disorders in patients with bowel disorders.

Section snippets

Animals

Male BALB/c mice (8–10 weeks old) were purchased from Harlan (Indianapolis, IN) and maintained under specific pathogen–free (SPF) conditions. Germ-free NIH Swiss and BALB/c mice (7–9 weeks old), obtained from the Farncombe Gnotobiotic Unit of McMaster University, were colonized by gavaging fresh cecal contents from SPF BALB/C and NIH Swiss donors (obtained from the Central Animal Facility of McMaster University). They were housed in ultraclean conditions using ventilated racks. All mice were

Antimicrobial Treatment Induces Changes in the Gut Microbiota

To test whether altering the established intestinal microbiota alters mouse behavior, we administered a mixture of nonabsorbable ATMs or sterile water for 7 days to BALB/c SPF mice. A combination of culture and molecular-based approaches were used to identify changes in the intestinal microbiota. Because many bacteria cannot be cultured, 16S ribosomal RNA targeted polymerase chain reaction–DGGE and sequencing was used to examine microbiota composition. Before treatment, DGGE profiles were

Discussion

The results of this study provide strong evidence for a microbiota–gut–brain axis that influences brain biochemistry and modulates behavior in adult mice. This is supported by several lines of evidence. First, transient perturbation of the microbiota increased hippocampal BDNF and exploratory behavior. Second, these changes were reversible upon normalization of the microbiota after withdrawal of the ATM. Third, ATM administration did not alter behavior in germ-free mice. Fourth, we showed that

Acknowledgments

The authors are grateful to Mr Paul Malinowski for technical assistance.

P.B. and E.D. contributed equally to this manuscript.

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    Conflicts of interest These authors disclose the following: S. M. Collins, P. Bercik, and E. F. Verdu received grant support from Nestle Switzerland. The remaining authors disclose no conflicts.

    Funding Supported by Canadian Institutes for Health Research and Crohn's and Colitis Foundation of Canada grants (S.M.C., P.B.); E. F. Verdu and Premysl Bercik hold Internal Career Research Awards from the Department of Medicine at McMaster University.

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