Maternal Separation Pups Research Articles

Neonatal maternal separation of rat pups results in abnormal cholinergic regulation of epithelial permeability

Neonatal maternal separation (MS) predisposes adult rats to develop stress-induced mucosal barrier dysfunction/visceral hypersensitivity and rat pups to develop colonic epithelial dysfunction. Our aim was to examine if enhanced epithelial permeability in such pups resulted from abnormal regulation by enteric nerves. Pups were separated from the dam for 3 h/day (days 4-20); nonseparated (NS) pups served as controls. On day 20, colonic tissues were removed and mounted in Ussing chambers. Horseradish peroxidase (HRP) flux was used to measure macromolecular permeability. HRP flux was increased in MS versus NS pups. The enhanced flux was inhibited by the cholinergic muscarinic antagonist atropine and the nicotinic antagonist hexamethonium. The cholinergic component was greater in tissues from MS versus NS pups, suggesting that increased cholinergic activity was responsible for the MS elevated permeability. Western blots and immunohistochemistry of colonic tissues demonstrated increased expression of choline acetyltransferase (ChAT) in MS pups, indicating greater synthesis of acetylcholine. Since a previous study indicated that corticotrophin-releasing factor (CRF) mediates barrier dysfunction in MS pups, we examined if the two pathways were linked. In MS tissues, nonselective CRF receptor antagonism inhibited the enhanced flux, and the addition of atropine did not produce further inhibition. Using selective receptor antagonists, we identified that CRF receptor 2 was involved in mediating this effect. These findings suggest that CRF, via CRF receptor 2, acts on cholinergic nerves to induce epithelial barrier dysfunction. Our study provides evidence that MS stimulates synthesis of acetylcholine, which, together with released CRF, creates a condition conducive to the development of epithelial barrier defects.

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

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...

Neonatal Maternal Separation Causes Colonic Dysfunction in Rat Pups Including Impaired Host Resistance

Previous studies have shown that early life stress in the form of intermittent maternal separation (MS) predisposes adult rats to develop stress-induced intestinal mucosal dysfunction and visceral hypersensitivity. However, the mechanism involved in the functional abnormalities is unclear. Our aim was to study immature animals during or shortly after exposure to MS to determine whether there are early pathophysiological changes in the gut. Sprague-Dawley rat pups were individually separated from the dam for 3 h/d from 4 to 21 d of age; nonseparated (NS) control pups remained in the home cage with the dam. On d 19-20, d 24-25, and d 29-30, blood was collected for corticosterone measurement, and colonic tissues were removed for functional and morphologic assessment. Corticosteroid levels were elevated in MS pups compared with NS, indicating that MS was indeed stressful. The distal colon demonstrated significantly enhanced ion secretion and macromolecular permeability at d 19-20 and d 24-25, returning to normal by d 29-30. Electron microscopy and bacterial culture studies indicated bacteria adhering to and penetrating into the colonic epithelium of the MS pups at all time points, while such events were rare in NS pups. The pathophysiological changes were inhibited by injecting pups sc with a corticotropin-releasing hormone (CRH) receptor antagonist daily during MS. Our studies indicate that early psychological trauma predisposes neonatal rats to develop persistent mucosal barrier dysfunction, including impaired host defense to luminal bacteria, by a mechanism involving peripheral CRH receptors.

O0028 NEONATAL MATERNAL SEPARATION INDUCES LONG-LASTING DISTAL COLONIC MUCOSAL BARRIER DYSFUNCTION AND ALTERED BACTERIAL-EPITHELIAL INTERACTIONS IN RAT PUPS

Introduction: Our previous studies have shown that early life stress in the form of intermittent maternal separation (MS) predisposes adult rats to develop intestinal mucosal dysfunction, specifically defective barrier function, following exposure to a mild acute stressor. Despite such findings, the immediate consequences of early life stress in neonatal rat pups have not been examined. Methods: Sprague-Dawley (SD) rat pups were individually separated from their mother for 3h/day from 4–20 days of age, while control non-separated pups (NS) remained with their dam. Studies were conducted on days 19–20, 24–25 and 29–30 when blood was collected for corticosterone measurement, and colonic tissues were removed for functional and morphological assessment. Tissues were mounted on Ussing chambers where baseline ion transport (indicated by short circuit current, Isc), and macromolecular permeability (flux of horseradish peroxidase, HRP) were assessed. Electron microscopy (EM) photomicrographs were analyzed for epithelial abnormalities. Results: Intermittent separation caused stress as indicated by elevated corticosteroid levels in serum of MS pups compared to controls. There was a higher baseline value for Isc in the distal region of the colon compared to the proximal region in all pups. Ion secretion in the distal colon was stimulated significantly in MS pups compared to controls at 19–20 and 24–25, but not at 29–30 days of age. More dramatically macromolecular uptake was enhanced 3-fold in the distal colon of MS pups compared to NS controls at 19–20 days of age, with normalization occurring by 29–30 days of age. EM studies of this region showed bacteria adhering to and penetrating into the epithelium of the MS pups, while such organisms were absent in the NS group in all age groups. Conclusion: Early psychological trauma predisposes pre-weanling rat pups to develop mucosal barrier dysfunction which involves lack of protection from adhering/internalizing bacteria. This dysfunction persists long after weaning. We speculate that abnormal bacterial-epithelial interactions in early life may result in altered tolerance to commensal flora and may predispose affected individuals to develop microbial-induced inflammation in later life.