Auswirkungen extrinsischer Denervierung auf die NANC-Innervation mit Substance P und VIP in der longitudinalen Muskulatur des Jejunums in der Ratte

Abstract

Introduction: Extrinsic denervation of the transplanted small bowel could play a substantial role in enteric motor dysfunction of the transplanted gut. The aim of this study was to determine effects of extrinsic denervation on motor function mediated by the nonadrenergic, noncholinergic (NANC) neurotransmitters Substance P (Sub P) and Vasoactive intestinal polypeptide (VIP). Methods: Jejunal longitudinal muscle strips were obtained from 6 groups of Lewis rats (n > 6/group): NC (naive controls); SC (sham operated rats); 1 and 8 weeks after jejunal and ileal intestinal transection/anastomosis to disrupt enteric myoneuronal continuity (TA-1 and TA-8), and after syngeneic jejunoileal transplantation (SBT-1 and SBT-8). We studied the effect of exogenous Sub P and VIP (10−8; 10−7; 10−6M) on spontaneous contractile activity under NANC-conditions and evaluated antagonistic properties of [D-Pro2,D-Trp7,9]-Sub P (Sub P antagonist) and [D-p-Cl-Phe6,Leu17]-VIP (VIP antagonist) with and without NO-synthase inhibitor L-NG-nitro arginine (L-NNA). Data are Mean ± SEM in [%] of baseline contractile activity (defined as 100%). Results: Spontaneous contractile activity did not differ between groups. Sub P dose-dependently increased contractile activity in all groups, greater in NC compared to SBT-8 (355 ± 40 % vs. 177 ± 16 %; p < 0.01). Response to Sub P (10−6M) was less in SBT-8 compared with SBT-1 (177 ± 16 % vs. 322 ± 22 %; p = 0.001). [D-Pro2,D-Trp7,9]-Sub P actually stimulated contractile activity in the NC, SBT-1, and SBT-8 (130 ± 3 %, 124 ± 4 %, and 132 ± 5 %, resp.; p < 0.01) but did not block the effect of 10−7M Sub P. VIP dose-dependently decreased contractile activity in all groups 1 week postoperatively (SC: 63 ± 8 %; TA-1: 57 ± 7 %; SBT-1 55 ± 9 %; p < 0.01); effect of VIP was greater in SBT-1 vs. SBT-8 (55 ± 9 % vs. 93 ± 7 %; p < 0.01). L-NNA reduced the inhibitory effect of VIP (10−6M) in all groups where VIP had an effect, especially in TA-1 (57 ± 4 % vs. 83 ± 6 % (with L-NNA); p=0.001). In muscle strips precontracted with 10−7M Sub P, VIP (10−6M) markedly reduced contractile activity in all groups (13 ± 2 % to 21 ± 5 %; p < 0.01). The percentage inhibition caused by VIP (10−6M) was greater than the inhibition of spontaneous contractile activity (p < 0.01). In precontracted muscle strips, [D-p-Cl-Phe6,Leu17]-VIP reversed the inhibition of VIP in SC, TA-1, TA-8, and SBT-8 (71 ± 5 % to 84 ± 6 %; p < 0.005); without precontraction [D-p-Cl-Phe6,Leu17]-VIP had no effect. Conclusions: Chronic extrinsic denervation causes a decrease in contractile response to Sub P in rat jejunal longitudinal muscle. Abdominal operations increase VIP sensitivity, which is reversible after 8 weeks. Precontraction with Sub P increases inhibitory effects of VIP. Effect of VIP seems mediated in part by NO.