Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression

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Ingestion of Lactobacillus strain regulates emotional behavior and

central GABA receptor expression in a mouse via the vagus nerve.

<http://www.ncbi.nlm.nih.gov/pubmed/21876150>

Bravo JA, Forsythe P, Chew MV, Escaravage E, Savignac HM, Dinan TG,

Bienenstock J, Cryan JF.

Proc Natl Acad Sci U S A. 2011 Aug 29.

There is increasing, but largely indirect, evidence pointing to an

effect of commensal gut microbiota on the central nervous system (CNS).

However, it is unknown whether lactic acid bacteria such as

Lactobacillus rhamnosus could have a direct effect on neurotransmitter

receptors in the CNS in normal, healthy animals. GABA is the main CNS

inhibitory neurotransmitter and is significantly involved in regulating

many physiological and psychological processes. Alterations in central

GABA receptor expression are implicated in the pathogenesis of anxiety

and depression, which are highly comorbid with functional bowel

disorders. In this work, we show that chronic treatment with L.

rhamnosus (JB-1) induced region-dependent alterations in GABA(B1b) mRNA

in the brain with increases in cortical regions (cingulate and

prelimbic) and concomitant reductions in expression in the hippocampus,

amygdala, and locus coeruleus, in comparison with control-fed mice. In

addition, L. rhamnosus (JB-1) reduced GABA(A?2) mRNA expression in the

prefrontal cortex and amygdala, but increased GABA(A?2) in the

hippocampus. Importantly, L. rhamnosus (JB-1) reduced stress-induced

corticosterone and anxiety- and depression-related behavior. Moreover,

the neurochemical and behavioral effects were not found in vagotomized

mice, identifying the vagus as a major modulatory constitutive

communication pathway between the bacteria exposed to the gut and the

brain. Together, these findings highlight the important role of bacteria

in the bidirectional communication of the gut-brain axis and suggest

that certain organisms may prove to be useful therapeutic adjuncts in

stress-related disorders such as anxiety and depression.