Effect of myenteric denervation on intestinal epithelium proliferation andmigration of suckling and weanling rats

The effects of myenteric denervation on the cell kinetics of the intestinal epithelium of suckling and weanling rats were investigated. The myenteric plexus of an ileal segment was partially ablated by serosal application of benzalkonium chloride (BAC) in three groups of rats: those that underwent s urgery at 13 days and were killed 15 (13/28-day-old) or 23 (13/36-day-old) days after treatment, and those that were operated at 21 days (21/36-day-ol d) and were killed 15 days after treatment. The extent of denervation was a ssessed in whole-mount preparations. The cell bodies of myenteric neurones were stained by NADH-diaphorase histochemical technique. Cell proliferation was estimated by the mitotic index (MI) and morphometric analysis of villu s and crypt lengths using an image analysis system. Thickness of the muscle layers was also assessed by morphometry, Cell migration on the villi was e stimated by the position of the leading labelled cell 24 h after tritiated thymidine injection. The number of neurones was reduced by around 80% in ra ts operated at 13 days, and reduced by 98% in those operated at 21 days. Th e thickness of the muscle layers was increased in all groups of treated ani mals. MI was significantly higher 15 days after BAG-treatment in the 13/28 group. Morphological changes in the intestinal mucosa were observed 15 days after BAG-treatment, when there was an increase in villus height (13/28 gr oup) and crypt depth (13/28 and 21/36 groups). Cell migration rate was acce lerated in the 21/36 group. No differences where found in the 13/36 group. These results show the strong effect of myenteric ablation on cell prolifer ation and migration in the ileal epithelium in the first 15 days of treatme nt in suckling and in weanling rats, and the subsequent recovery of intesti nal mucosa homeostasis later on.