The large intestine of the mammalian gastrointestinal tract contains trillions of microorganisms, an amount ten times greater than the total number of cells in the body. This diverse group of symbiotic bacteria, called the gut microbiome, is critical for mammalian survival and exerts a surprisingly powerful influence on the brain and behavior. Notably, there is emerging evidence that the gut microbiome and central nervous system communicate via the gut-brain axis, which involves a series of afferent and efferent pathways that regulate homeostasis and inflammation. In addition, disruption of the gut-brain axis has been associated with a suite of psychological and neurological disorders, including Parkinson’s disease, autism, anxiety, and depression.
Our lab has previously shown that disrupting the gut microbiome via antibiotic administration reduces aggressive behavior in a sex-specific manner. Specifically, male hamsters require two antibiotic treatments to show decreased levels of aggression, whereas female hamsters reduce aggressive behavior after a single antibiotic treatment. Furthermore, males recover to pre-treatment levels of aggression following a recovery period, whereas females do not. While these findings suggest that altering the gut microbiome affects aggressive behavior and its underlying physiological processes differently in males and females, the specific mechanisms that drive these sex differences in aggression have yet to be explored. In collaboration with graduate student Beth Morrison and Lauren Rudolph from Pomona College, I am investigating whether gut dysbiosis alters circulating and neural hormone profiles and the morphology of microglia, immune cells in the central nervous system that have been implicated in neurological diseases, in male and female hamsters and whether these physiological changes culminate in shifts in aggressive behavior.