Probiotic treatment of rat pups normalizes corticosterone release and ameliorates colonic dysfunction induced by maternal separation

Mélanie G Gareau ^1*, Jennifer Jury ¹, Glenda MacQueen ¹, Philip M Sherman ² and Mary H Perdue ¹

¹ McMaster University, Canada
² The Hospital for Sick Children, Canada

^* To whom correspondence should be addressed. E-mail: melanie.gareau{at}utoronto.ca.

Accepted 27 February 2007

Abstract

Background: We previously showed that neonatal maternal separation (MS) of rat pups causes immediate and long-term changes in intestinal physiology. AIM: To examine if administration of probiotics affects MS-induced gut dysfunction.

Methods: MS pups were separated from the dam for 3h/day from days 4-19; non-separated (NS) pups served as controls. Twice per day during the separation period, 10⁸ probiotic organisms (two strains of Lactobacillus species) were administered to MS and NS pups; vehicle-treated pups received saline. Studies were conducted on day 20, when blood was collected for corticosterone measurement as an indication of hypothalamic-pituitary-adrenal (HPA) axis activity, and colonic function was studied in tissues mounted in Ussing chambers. Ion transport was indicated by baseline and stimulated short-circuit current (Isc); macromolecular permeability was measured by flux of horseradish peroxidase (HRP) across colonic tissues; bacterial adherence/penetration into the mucosa was quantified by culturing tissues in selective media. Colonic function and host defense were also evaluated at day 60.

Results: Isc and HRP flux were significantly higher in the colon of MS vs NS pups. There was increased adhesion/penetration of total bacteria in MS pups, but a significant reduction in Lactobacillus species. Probiotic administration ameliorated the MS-induced gut functional abnormalities and bacterial adhesion/penetration both at day 20 and 60, and reduced the elevated corticosterone levels at day 20.

Conclusions: Our results indicate that altered enteric flora are responsible for colonic pathophysiology. Probiotics improve gut dysfunction induced by MS, at least in part by normalization of HPA axis activity.

Keywords: Barrier function, Neonate, Stress

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