Effect of noise on the morphology of the intestinal mucosa in laboratory rats

To determine whether noise-induced stress disrupts the intestinal mucosa of laboratory rats, one group of 8 rats ("noise" rats) was subjected to 15 min of white noise (90 dB) daily for 3 wk. Another group ("quiet"rats) was housed for 3 wk in an acoustically similar room but with no additional noise. A 3rd group ("recovery" rats) was housed in the noise room for 3 wk and then in the quiet room for a further 3 wk. The ilea were fixed for microscopy. Villi adjacent to Peyer patches showed significantly more degranulated mast cells (mean+/-standard error of the mean, 3.95+/-0.80 versus 0.35+/-0.29, respectively) and eosinophils (mean+/-standard error of the mean, 9.46+/-0.44 versus 4.58+/-0.38) per villus section in noise rats than in quiet rats. Similar results were obtained with rooms reversed, to account for any differences in room characteristics. The mean width of villus laminar propria was significantly greater in noise rats than quiet rats, suggesting edema. In addition, mucosal epithelial cells of noise rats were often separated, sometimes detaching from the basement membrane, whereas those of quiet rats were intact. Behaviorally, noise rats exhibited significantly more grooming and rearing than quiet rats. Compared with noise rats, recovery rats showed no reduction in mast cell degranulation or mean width of villus lamina propria, but there were increased numbers of secreting goblet cells in villi adjacent to Peyer patches and some recovery of epithelial integrity.