Sprouting of bladder nerves into cystoplastic cecal segment in the rat

Incorporation of bowel into the bladder (enterocystoplasty) has been widely used to increase bladder capacity. It has been reported by others that the response of smooth muscle from the cystoplastic segment of the intestine s hifts from that of the intestine (relaxation to alpha-agonists and ATP) to that of the bladder (contraction to alpha-agonists and ATP). This suggests a functional integration of the intestinal muscle into the bladder; the mec hanisms are unknown. The aims of the present study were (1) to elucidate if there are signs of bladder nerves sprouting across the anastomosis into th e intestinal segment, and (2) to study what happens with the intrinsic inne rvation of the intestinal segment. As a model, we used cecocystoplasty in r ats. The bladder was opened and a patch of cecum with intact vascular suppl y was anastomosed to the bladder. After two to 11 months the rats were sacr ificed and the bladders mounted as wholemounts and stained for acetylcholin esterase-containing nerves, or embedded in paraffin for histology. A pronou nced degeneration of the myenteric plexus was found in the cecal segments. In some areas, this had proceeded to the extent that the ganglia were isola ted ovoid lumps of cells with no apparent connection to other ganglia. Area s lacking ganglia and nerve trunks but still with muscle could be found in all specimens. Abundant axon bundles were demonstrated sprouting from the c ut bladder nerves close to the anastomosis, The bundles spread out in a fan -like pattern or were organized as fewer thicker nerves. There were many ne rve bundles entering the cecal segment where they branched and the diameter decreased till they no longer became visible. Some nerves reached survivin g lumps of myenteric ganglion cells. The results show that the bladder nerv es sprout into the anastomosed cecal segment. It is reasonable to assume th at these nerves are responsible for the changes in receptor pharmacological properties of the cecal smooth muscle towards that of bladder muscle.