Long-term effects of small bowel transplantation on intestinal motility.

We previously found that the contractile motility of the jejunum was increased 4 weeks after transplantation, and that the dominant intrinsic neural component was changed from cholinergic to nonadrenergic, noncholinergic (NANC). The present study investigated the long-term effects of transplantation on jejunal motility using rats that survived for 2 years after surgery. Jejunal strips were harvested from various groups of rats, and intestinal motility was assessed by electrical transmural stimulation. Stimulation produced a similar increase of contraction at 4 weeks and 2 years after grafting. Pretreatment with atropine showed that the cholinergic component of contraction was 45%, 24%, 32%, and 24% in controls, rats 4 weeks after transplantation, 2-year-old controls, and rats 2 years after transplantation, respectively. The NANC component (obtained with atropine and guanethidine) in each group was, respectively, 56%, 73%, 60%, and 69%. The actual value of the tetrodotoxin-insensitive myogenic component was significantly increased at 2 years after transplantation. A substance P antagonist ([Arg6, D-Trp7,9, Mephe8], substance P 6-11), inhibited most of the NANC contraction after transplantation. These results suggested that substance P has a key role in the motility of transplanted small bowel throughout the life of the grafts.