Abnormalities of nerve fibers in the circular muscle of patients with slow transit constipation.

Abnormalities of the enteric nervous system are thought to explain the pathophysiology of motility disorders. Our aim was to determine if particular classes of enteric neurons are affected in slow transit constipation (STC). Specimens were taken from the terminal ileum and ascending, transverse and descending colon of patients undergoing subtotal colectomy for STC. Immunohistochemistry was performed using antisera to neuron-specific enolase, tachykinin, leu-enkephalin, choline acetyltransferase, vasoactive intestinal peptide, nitric oxide synthase, tyrosine hydroxylase and neuropeptide Y. The density of nerve fibres labelled with these antibodies in each layer was compared with age-matched controls. The density of nerve fibres with tachykinin and enkephalin immunoreactivity was reduced in the colonic circular muscle of the 15 patients with STC, whereas innervation of all other layers was normal. This reduction of tachykinin-immunoreactive nerve fibres also occurred in nine of the 12 specimens of terminal ileum examined. No difference was detected in the density or distribution of nerve fibres using the other antisera. Excitatory nerve fibres are present in the circular muscle in STC but they are deficient in tachykinins and enkephalin.