The mechanism of intestinal motility in homozygous mutant Ncx/Hox11L.1-deficient mice--a model for intestinal neuronal dysplasia.

PURPOSE: Homozygous mutant Ncx/Hox11L.1-deficient (Ncx-/-) mice develop mega-ileo-ceco-colon with a caliber change in the proximal colon. This study investigated the mechanism of intestinal motility in these mice.

METHOD: Five-week-old male and female Ncx-/- mice with mega-ileo-ceco-colon (n = 8) were compared with age-matched male BDF1 mice used as controls (n = 8). All mice were sacrificed, and uniform-sized strips of jejunum, ileum, proximal colon, and distal colon were exposed to electrical field stimulation and pretreatment with atropine sulfate, guanethidine, or tetrodotoxin. Contractile responses were recorded and compared.

RESULTS: Longitudinal muscle from strips of jejunum and ileum from all mice (BDF1 and Ncx-/-) did not respond to electrical field stimulation, whereas ileal circular muscle contracted in BDF1 mice and contracted and relaxed in Ncx-/- mice. Pretreatment with atropine sulfate and guanethidine inhibited the responses of circular muscle of distal colon and ileum in BDF1 mice significantly (P < .05), but no effect was observed in Ncx-/- mice.

CONCLUSION: In ileum, BDF1 mice have cholinergic and adrenergic dominant contraction patterns, whereas Ncx-/- mice have relaxation-dominant patterns because of nonadrenergic, noncholinergic nerves. Based on this, there would appear to be some kind of variation in the gastrointestinal nerve supply in Ncx-/- mice.