Role of nitric oxide in the colon of patients with slow-transit constipation

The cause of dysmotility in patients with slow-transit constipation is unknown. Nitric oxide has recently been shown to be a neurotransmitter in the nonadrenergic, noncholinergic inhibitory nerves of the human gut. To clarify the physiologic significance of nitric oxide in the colon of patients with slow-transit constipation, we investigated the enteric nerve responses in lesional and normal bowel segments derived from patients with slow-transit constipation and patients who underwent colon resection for colonic cancers.

Twenty-six preparations were taken from colonic lesions in eight patients with slow-transit constipation (2 men; age, 23 to 69 (mean, 44.8) years). Forty-two preparations were taken from the normal colons of 14 patients with colonic cancer (8 men; age, 40 to 66 (mean, 52.4) years). A mechanographic technique was used to evaluate in vitro muscle responses to electric field stimulation before and after treatment with various autonomic nerve blockers, NG-nitro-L-arginine, and L-arginine.

The colons of patients with slow-transit constipation were more strongly innervated by nonadrenergic, noncholinergic inhibitory nerves than were normal colons (P <0.05). Nitric oxide was found to act on both normal and slow-transit constipation colons. The colons of patients with slow-transit constipation were more strongly innervated by nitric oxide nerves than were normal colons (P < 0.01). Responses to electric field stimulation were the same in each case among the normal colons and were also the same in each case among the slow-transit constipation colons.

These findings suggest that an increase of nitric oxide mediates nonadrenergic, noncholinergic inhibitory nerves and plays an important role in the dysmotility observed in the colons of patients with slow-transit constipation.