Changes of cholinergic and nitrergic system of defunctionalized colon after colostomy in the rabbit

YABANCI D LDE ÖZET (SUMMARY)Transient or permanent colostomy is widely used as an option of treatment inpaediatric and adult surgery. In children it is mostly used as a first stage procedure inHirschsprung?s disease and anorectal malformation. It is also performed as a prevention incolorectal surgery to secure the distal colonic anastomosis and as a transient procedure inemergency surgery to decrease the risk of anastomotic breakdown. Althougth it is widely usedin surgical practice the affect of the colostomy on the innervation and the motility of the distalbowel isn?t known clearly. In this study we evaluated the affect of the colostomy oncholinergic and nitrergic systems of the distal colon with an in-vitro method.In this study two months old New Zealand rabbits were used. The animals wererandomly allocated into two groups: control (n=8), study (n=12). The rabbits were operatedon under sterile conditions. A sigmoid colostomy were performed to the rabbits of the studygroups and distal bowel were closed as Hartmann and left in the peritoneal cavity. After twomonths of waiting period colon segments were harvested and rabbits were sacrificedthereafter. In the control group the segments from the same part of the colon were harvestedfor invitro experiments when the rabbits become four months old. In the invitro part of theexperiment the isolated circular muscle strips which were prepared from the harvested distalcolon were used. First the contraction and relaxation responses of the smooth muscles aredetected by using KCl and papaverine as smooth muscle stimulant agents. Then theneurologic responses of the muscle strips to the electrical field stimulation (EFS) wereevaluated in an environment with guanethidine and indomethacin. These responses wereaccepted as neurological responses when they were disappeared after adding tetrodotoxin inthe environment. Then the EFS studies were repeated in atropine, L-NAME, atropine and L-NAME added environments. To evaluate the affect on the postsynaptic receptors, carbacholevoked contraction responses and sodium nitroprusside(SNP), sildenafil and L-argininederived relaxation responses recorded.As a result although macroscopic athrophy had developed in the distal colonicsegment of the colostomy, the contraction and relaxation capacity of the smooth muscles didnot change. However, the presynaptic secretion of the neurotransmitters such as acetylcholine,nitric oxide and neuropeptides were diminished. Though the contraction capacity of thesmooth muscle was not affected, the motility of the distal colon was deteriorated by thedefective secretion of the presynaptic neurotansmitters. We believe that further investigationwill be needed to evaluate the possibility to cure this motility disorder.