Effects of neuropeptides on smooth muscle contraction after small bowel transplantation.

We have previously shown that increased intestinal contraction after small bowel transplantation was associated with marked enhancement in the nonadrenergic, noncholinergic (NANC) intrinsic neural component. In the present study, we examined the effect of three NANC neurotransmitters (substance P, neurotensin, and cholecystokinin-octapeptide, CCK-OP) on jejunal longitudinal muscle strips after syngeneic total small bowel transplantation in rats. Fourteen rats were divided into a normal control group (n = 7) and a group tested 4 weeks after transplantation (n = 7). A superfusion system was used to evaluate the in vitro effects of the three neuropeptides in the presence of atropine and guanethidine. In the control group, maximum contractile response to substance P, neurotensin, and CCK-OP was 5.16 +/- 0.30, 1.46 +/- 0.15, and 1.13 +/- 0.17 mg tension/mg wet weight, respectively, while the values for the transplanted group were 5.71 +/- 0.29, 2.52 +/- 0.17, and 1.20 +/- 0.18 mg tension/mg wet weight. These results show that neurotensin-induced contraction increased significantly after transplantation, but substance P appeared to be the dominant NANC neurotransmitter in both normal and transplanted small bowel.