Long-term role of nitric oxide in the enteric nervous system of the transplanted rat intestine

Abstract

We investigated the long-term changes of the nitric oxide (NO)-related neural component after syngeneic total small bowel transplantation in rats. In the present study, the NO-related neural component was examined using the electrophysiological and NADPH-diaphorase histochemical technique. The rats were divided into four groups: an untreated young adult control group, an untreated 2-year-old control group, a group killed 1 month after transplantation, and a group killed 2 years after transplantation. A superfusion apparatus was used to evaluate the response of jejunal strips to electrical transmural stimulation. In the presence of adrenergic and cholinergic blockade, the inhibitory effect of l-N^G-nitro arginine (l-NNA; a nitric oxide synthesis inhibitor) on nonadrenergic, noncholinergic (NANC) relaxation was expressed as a l-NNA-sensitive component. The l-NNA-sensitive component accounted for 41.6 ± 4.6 % (mean ± SE), 43.1 ± 3.5 %, 54.6 ± 4.1 %, and 55.8 ± 3.5 % in the young control group, 2-year control group, 1-month transplant group, and 2-year transplant group, respectively, being significantly higher in the transplant groups (p < 0.05). The actual strength of the l-NNA-sensitive component was 0.24 ± 0.03 (mean ± SE), 0.26 ± 0.02, 0.44 ± 0.04, and 0.46 ± 0.04 mg of tension per mg of wet weight, respectively, also being significantly higher in the transplant groups (p < 0.001). In addition, the percentage of NADPH-diaphorase-positive fibers was 24.1 ± 1.1 % (mean ± SE), 25.5 ± 1.4 %, 31.0 ± 1.6 %, and 30.9 ± 2.0 %, respectively, being significantly higher in the transplant groups (p < 0.05). These results suggest that NO neurons in the intrinsic jejunal nervous system have an adaptive role in maintaining intestinal graft motility.