Are there any functional differences of the enteric nervous system between jejunum and ileum in normal humans?

BACKGROUND/AIMS Functional differences of the enteric nervous system (ENS) between the jejunum and ileum in humans are still unknown. To clarify the physiological differences of the ENS in the normal human jejunum and ileum, we investigated the enteric nerve responses on normal jejunum and normal ileum in vitro. METHODOLOGY Twenty-two preparations of normal jejunum were taken from 22 patients with gastric cancer (14 men and 8 women, aged 43 to 65 years with a mean age of 49.0 years). Twenty preparations of normal ileum were also taken from 20 patients with right sided colonic cancer (15 men and 5 women, aged 40 to 63 years with a mean age of 50.9 years). A mechanographic technique was used to evaluate in vitro muscle responses to electrical stimulation (EFS) of adrenergic and cholinergic nerves before and after treatment with various autonomic nerve blockers. RESULTS Responses to EFS before blockade of the adrenergic and cholinergic nerves; Muscle strips in jejunum and ileum demonstrated significant contraction reactions rather than relaxation reactions (p < 0.0001, p = 0.0001, respectively). In addition, jejunal muscle strips showed significant contraction reactions than those in ileal muscle strips (p = 0.0274). Responses to EFS after blockade of the adrenergic and cholinergic nerves; Jejunal muscle strips demonstrated relaxation reactions rather than contraction reactions by EFS (p = 0.0704). Ileal muscle strips significantly demonstrated relaxation reactions rather than contraction reactions by EFS (p < 0.0001). In addition, ileal muscle strips showed significant relaxation reactions more than those in jejunal muscle strips (p = 0.0451). Tetrodotoxin abolished the EFS responses in the muscle strips both jejunum and ileum. CONCLUSIONS Cholinergic nerves are mainly involved in regulation of enteric nerves in the jejunum rather than the ileum. In contrast, the ileum was more strongly innervated by non-adrenergic noncholinergic inhibitory nerves than the jejunum.