Background/aims: Non-adrenergic non-cholinergic inhibitory nerves are the most important nerves in the enteric nervous system of the human gut. Recently, it has been established that nitric oxide is released by stimulation of non-adrenergic non-cholinergic inhibitory nerves. Therefore, in order to evaluate the function of nitric oxide in the left-sided colon of patients with diverticular disease, we examined the enteric nerve responses in colonic tissues from patients with this disease, and also used the left-sided normal colon as a control.
Methodology: Colonic tissue specimens (the diverticular bearing segments) were obtained from 9 patients with diverticular disease of the left-sided colon, and normal segments of the left-sided colon were obtained from 16 patients with ascending colon cancer. A mechanograph was used to evaluate in vitro colonic responses to electrical field stimulation of adrenergic and cholinergic nerve before and after treatments with various autonomic nerve blockers, NG-nitro-L-arginine, and L-arginine.
Results: 1) The diverticular colon was more strongly innervated by cholinergic nerves than the normal colon (P < 0.01); 2) Non-adrenergic non-cholinergic inhibitory nerves were found to act on the normal colon and to a lesser extent in the diverticular colon (P < 0.05). 3) Nitric oxide mediates the relaxation reaction of non-adrenergic non-cholinergic inhibitory nerves in the normal colon and to a lesser extent in the diverticular colon.
Conclusions: These findings suggest that the intrinsic intestinal innervation contains excitatory and inhibitory nerves and that the former, especially cholinergic nerves, are dominant in the left-sided colon with diverticula. In addition, diminution of action of non-adrenergic non-cholinergic inhibitory nerves by substances such as nitric oxide may be largely related to the high intraluminal pressure by colonic segmentation observed in the left-sided colon with diverticula.