Researchers have found strong evidence of a link between specific brain behavior & the microbial life forms in the gut. Before we go further into the two experiments that were used, let’s get some terminology out of the way.
Some of the mice used were either Specific Pathogen Free(SPF) or germ-free. SPF means the mice do not have any specific pathogens in their systems, but they are not completely germ-free. Germ-free mice have been kept in a sterile environment since birth & thus do not have a built up immune system or microbial flora.
The types of mice used were either BALB/c or NIH Swiss mice. BALB/c actually stands for Bagg Albino, after Dr. Halsey J. Bagg who started breeding these mice back in the 1920s. NIH Swiss mice originated from Switzerland back in the 1920s, later making their way to the National Institute of Health in Maryland. BALB/c mice supposedly are known for being less exploratory than their NIH Swiss counterparts.
Brain-derived neurotropic factor(BDNF) is a protein found in the brain that acts on certain neurons in both the central & peripheral nervous system. It’s involved in maintaining the health of current neurons, facilitating growth of new neurons as well as playing a part in our ability to store long term memories. Low BDNF levels have been the subject of studies regarding brain disorders like depression, Alzheimer’s & schizophrenia.
Now on to the two different tests that were done.
In the first experiment researchers gave antimicrobial drugs to both SPF & germ-free BALB/c mice. The SPF mice’s microbial flora changed due to this & the researchers witnessed increased exploratory behavior & higher levels of BDNF. The germ-free mice did not see such changes.
In the second experiment germ-free BALB/c mice were given microbial flora from SPF NIH Swiss mice. The, previously, germ-free BALB/c mice were later seen with increased exploratory behavior. The reverse was then done where germ-free NIH Swiss mice were given microbial flora from SPF BALB/c mice. The, previously, germ-free NIH Swiss mice were seen to have lowered exploratory behavior. Essentially it appears that changing the microbial flora affects the behavior of the animal.
Overall the research is interesting & may lead to more research into the link between the brain & the gut. It suggests that impacts to the gut may very well impact someone’s mental health, whereas in the past most would have put it down the other way around. It may not actually be “all in your head’, it might actually be “in your gut” after all.
1. Research Institutes: McMaster University, Michael G. DeGroote School of Medicine, Farncombe Family Digestive Health Research Institute