The concept that intestinal microbial composition not only affects the health of the
gut, but also influences centrally-mediated systems involved in mood, is supported
by a growing body of literature. Despite the emergent interest in brain-gut communication
and its possible role in the pathogenesis of psychiatric disorders such as depression,
particularly subtypes with accompanying gastrointestinal (GI) symptoms, there are
few studies dedicated to the search for therapeutic solutions that address both central
and peripheral facets of these illnesses. This study aims to assess the potential
benefits of the probiotic Bifidobacterium infantis in the rat maternal separation
(MS) model, a paradigm that has proven to be of value in the study of stress-related
GI and mood disorders. MS adult rat offsprings were chronically treated with bifidobacteria
or citalopram and subjected to the forced swim test (FST) to assess motivational state.
Cytokine concentrations in stimulated whole blood samples, monoamine levels in the
brain, and central and peripheral hypothalamic-pituitary-adrenal (HPA) axis measures
were also analysed. MS reduced swim behavior and increased immobility in the FST,
decreased noradrenaline (NA) content in the brain, and enhanced peripheral interleukin
(IL)-6 release and amygdala corticotrophin-releasing factor mRNA levels. Probiotic
treatment resulted in normalization of the immune response, reversal of behavioral
deficits, and restoration of basal NA concentrations in the brainstem. These findings
point to a more influential role for bifidobacteria in neural function, and suggest
that probiotics may have broader therapeutic applications than previously considered.
Copyright © 2010 IBRO. Published by Elsevier Ltd. All rights reserved.