Distributions of substance P- and VIP-immunoreactive nerve fibres in the colonic circular muscle in children.

In children with severe chronic constipation, abnormal distribution of substance P (SP) and vasoactive intestinal peptide (VIP), which represent excitatory and inhibitory nerves, respectively, has been reported. The normal distribution of these neuropeptides, however, is not well known. The aim of this study was to determine the populations of SP- and VIP-immunoreactive nerve fibres in the circular muscle of the colon in children. Surgically resected specimens were collected from a 6-year-old girl with familial polyposis coli (total colon) and nine patients with anorectal malformations aged 0-4 years (sigmoid colon). Double-labelling immunofluorescence was employed using neuron-specific enolase (NSE) with SP and NSE with VIP to count the percentage of SP- or VIP-labelled nerve fibres. These specimens showed normal submucous and myenteric plexuses stained with NSE. The population of SP- immunoreactive fibres was 15%-21% throughout the colon, and VIP was 39% in the caecum and 63%-65% in the transverse, descending, and sigmoid colon. In the four neonatal specimens (day 1 to 4), the SP population was only 1%-6% and the VIP population was also low (22%-33%). After 3 weeks of age, the populations had stabilised at 18%-26% for SP and 52%-62% for VIP. SP-immunoreactive nerve fibres were scarce in the neonatal period, and showed a rapid increase by 3 weeks and a similar though less dramatic increase in VIP-immunoreactive fibres. VIP-immunoreactive fibres were fewer in the caecum that at other colonic levels, where they accounted for 60% of NSE-labelled fibres; the SP population, however, was comparable at all levels of the colon at about 20% of NSE-labelled fibres.