Changes of intestinal motility after small bowel transplantation in the rat

Small bowel transplantation disturbs the enteric neural network as a result of complete extrinsic denervation, but few data are available on the status of the intrinsic neurons in intestinal grafts. This study assessed intestinal motility and the intrinsic innervation of jejunal longitudinal muscle after transplantation in rats using electrical transmural stimulation. Syngeneic total small bowel transplantation was performed in male Lewis rats using microsurgical techniques. The rats were divided into four groups-i.e., a control group and groups examined at one (G1), two (G2), and four (G4) weeks after transplantation. Jejunal strips were mounted in a superfusion apparatus for examination. Functional innervation was assessed by comparing contraction and relaxation following stimulation at 10 Hz with or without various drugs. All grafts showed increased contractile motility when compared with the control group. The cholinergic excitatory components in the control, G1, G2, and G4 groups were 45%, 73%, 66%, and 24%, respectively, while nonadrenergic noncholinergic-excitatory components were 56%, 53%, 57%, and 78%. Thus, there was a marked change in excitatory innervation after transplantation. However, the tetrodotoxin-insensitive (myogenic) component showed no changes in active tone after transplantation. Adrenoceptor antagonists had a decreased effect on all grafts except for yohimbine (an alpha 2 blocker). The contractile motility of transplanted jejunum was increased compared with that of the control bowel. However, the dominant intrinsic component varied with the time after transplantation.