Effect of Massive Small Bowel Resection on Components of the Peptidergic Innervation of the Rat Small Intestine

The effect of massive small bowel resection on the immunostaining of neuropeptides in the submucous plexus of the retained small intestine was examined. The neuropeptides chosen were somatostatin and vasoactive intestinal polypeptide because these are markers for two of the major populations of neurons in the plexus. Three different methods were used to assess the effect of resection on the enteric nervous system. Firstly immunocytochemical staining of neuropeptide containing neurons and nerve fibers was compared between test and control animals. The results demonstrated a significant increase in the number and size of the vasoactive intestinal polypeptide containing neurons with no change in the number of somatostatin neurons although these were also increased in size. Secondly the possibility that the increase in neuron number might be the result of neuronal division was examined by 3H-thymidine incorporation experiments. The results demonstrated that no neuronal elements were labelled. Finally the possibility that the increase in vasoactive intestinal peptide was the result of an increase in transcription was assessed by Northern blot analysis. The results demonstrated a small but significant increase in mRNA levels. It was concluded that massive small bowel resection directly affects neuropeptide levels in the submucous plexus, resulting in an increase in vasoactive intestinal polypeptide-immunoreactive neurons.