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

Abstract

Gareau MG, Jury J, Perdue MH. Neonatal maternal separation of rat pups results in abnormal cholinergic regulation of epithelial permeability. Am J Physiol Gastrointest Liver Physiol 293: G198-G203, 2007. First published May 17, 2007; doi:10.1152/ajpgi.00392.2006.-Neonatal maternal separation (MS) predisposes adult rats to develop stressinduced 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. stress; colonic; barrier THE NEONATAL PERIOD is an important developmental period in humans and rodents, and stress during this time can have long-lasting effects on behavior and physiology. Maternal separation (MS) is a well-characterized model of early life stress used in the study of anxiety and depression (17, 31) as well as intestinal dysfunction (1,2,7,28,37). The physiological response to stress is controlled by the hypothalamicpituitary adrenal (HPA) axis, which develops during the neonatal period. Exposure to stress during this time results in the formation of a dysregulated axis with a compromised ability to downregulate the synthesis of corticotrophin-releasing factor (CRF), a key stress hormone (26).Adult rats of a stress susceptible strain that are subjected to daily separation from the dam during the neonatal period demonstrate increased colonic permeability (2) and visceral hyperalgesia (28). Adult rats that are not genetically susceptible t...

Role of Corticotropin-releasing Factor in Gastrointestinal Permeability

“…79 Stress-induced enhancement of colonic permeability was mimicked by exogenous administration of CRF, 33 and abolished by pretreatment with the peripheral administration of the non-selective CRF antagonists astressin or -helical CRF 9-41 . 37,55,80 Likely, the selective CRF 1 receptor agonist, cortagine, 48 the selective CRF 1 receptor antagonist, SSR-125543, 80 and the selective CRF 2 receptor antagonist, antisauvagine-30, 78 reduced the response, supporting the participation of both CRF receptors in the modulation of colonic permeability.…”

“…23 This increase was glucocorticoid-mediated because adrenalectomy and pharmacologic blockade of glucocorticoid receptors inhibited the response, and dexamethasone increased gastrointestinal permeability in control rats. 23 Similarly, rats models of chronic stress (maternal deprivation, 55,[77][78][79] WAS, 45 and crowding stress 52 ) also show increased ionic permeability, and macromolecular permeability throughout the intestine. The increase was mediated partly by mechanisms including, muscarinic and nicotinic pathways, activation and number of mast cells and the release of nerve growth factor.…”

The Role of Intestinal Barrier Function in Early Life in the Development of Colitis

“…Stress induced in early life by neonatal maternal separation may affect colonic permeability and motility Coutinho et al, 2002;Gareau et al, 2007). When this condition is mimicked in a rat model of IBS, colonic smooth muscle contraction amplitude is increased and this is associated with an increased expression of L-type calcium ion channels in colonic smooth muscle, as the level of calcium in smooth muscle cells increased in response to Ltype calcium ion channel activation .…”

Glucocorticoids and the Intestinal Environment

“…They also showed in following experiments that the levels of brain-derived nerve factor (BDNF), norepinephrine and 5-5-hydroxytryptamine (5-HT) in the cortex and hippocampus were significantly lower in GF mice than in SPF mice [188]. Improvements of stress-related symptoms by probiotic administration also support the possible regulatory effects of microbiota on HPA axis and brain functions [44,189]. Gareau et al [44] reported that probiotic treatments improved colonic dysfunction and corrected the higher corticosterone levels in stressed rats induced by maternal seperation.…”

“…Early life stress models such as maternal deprivation of pups from the dams have also been widely used [31,41,43,44], because stressful events in the early period of life (in the form of abuse, neglect or loss of the primary caregiver) have been shown to modify adult immune and gastrointestinal tract functions [12].…”