Physiological studies on nitric oxide in the right sided colon of patients with diverticular disease

Previously, we reported that non-adrenergic non-cholinergic (NANC) inhibitory nerves are decreased in the left-sided colon of patients with diverticular disease, contributing to their intraluminal high pressure by segmentation (1). It is established that nitric oxide (NO) is released by stimulation of NANC inhibitory nerves. Among Oriental people, including the Japanese, right-sided diverticular disease has predominated more frequently than among Western people. In order to evaluate the function of NO in the right-sided colon of patients with diverticular disease, we examined the enteric nerve responses in colonic materials from patients with this disease, using the right-sided normal colon as a control.

Colonic tissue specimens were obtained from 8 patients with diverticular disease of the right-sided colon, and normal segments of the right-sided colon were obtained from 11 patients with localized diseases. A mechanograph was used to evaluate in vitro colonic responses to electrical field stimulation (EFS) of adrenergic and cholinergic nerves before and after treatment with various autonomic nerve blockers, N(G)-nitro-L-arginine (L-NNA), and L-arginine.

1) Cholinergic nerves were more dominant in the diverticular colon than in the normal colon (p<0.01). 2) NANC inhibitory nerves were found to act on the normal colon and to a lesser extent in the diverticular colon (p<0.05). 3) NO mediates the relaxation reaction of NANC inhibitory nerves in the normal colon and to a lesser extent in the diverticular colon.

The intrinsic intestinal innervation contains excitatory and inhibitory nerves and the former, especially cholinergic nerves, are dominant in the right-sided colon with diverticula. In addition, reduction of the action of NANC inhibitory nerves by substances such as NO may be largely related to the tight intraluminal pressure by colonic segmentation observed in the right-sided colon with diverticula.