Weaning in the piglet is a stressful event associated with gastrointestinal disorders and increased disease susceptibility. Although stress is thought to play a role in postweaning intestinal disease, the mechanism by which stress influences intestinal pathophysiology in the weaned pig are not understood. The objective of these experiments was to investigate the impact of weaning on gastrointestinal health in the pig and to assess the role of stress signaling pathways in this response. Nineteen-day-old pigs were weaned and mucosal barrier function and ion transport were assessed in jejunal and colonic tissues mounted on Ussing chambers. Weaning caused marked disturbances in intestinal barrier function, demonstrated by significant (P<0.01) reductions in transepithelial electrical resistance (TER) and increases in intestinal permeability to ³H-mannitol in both the jejunum and colon as compared with intestinal tissues from age-matched, unweaned control pigs. Weaned intestinal tissues exhibited increased intestinal secretory activity as demonstrated by elevated short circuit current (I_sc) that was sensitive to treatment with tetrodotoxin and indomethacin suggesting activation of enteric neural and prostaglandin synthesis pathways in weaned intestinal tissues. Western analyses of mucosal homogenates showed increased expression of corticotrophin releasing factor (CRF) receptor 1 in the jejunum and colon of weaned intestinal tissues. Pre-treatment of pigs with the CRF receptor antagonist, -helical CRF (9-41) injected intraperitoneally 30-minutes prior to weaning, abolished the stress-induced mucosal changes. Our results indicate that weaning stress induces mucosal dysfunction mediated by intestinal CRF receptors, and activated by enteric nerves and prostanoid pathways.