Effect of neurotensin on colorectal motor and sensory function in humans

Animal studies have shown that neurotensin stimulates colonic motility, but little is known on the effect on rectocolonic function in humans. This study was designed to investigate the effect of neurotensin on rectal and colonic motor and sensory function and colonic reflexes in humans.

Motor and sensory function of the descending colon and rectum were studied in eight healthy volunteers (5 females; age range, 20-58 years) by using a dual, computerized, rectocolonic, barostat assembly. Measurements were performed during placebo and neurotensin infusion (5 pmol/kg per minute), respectively. Compliance and reflex mechanisms were assessed in both rectum and descending colon. Symptom perception (urge and pain) was scored using Visual Analog Scales (0-10 cm).

Neurotensin significantly (P < 0.05) increased rectal compliance (from 9 +/- 1.1 to 10.1 +/- 1.1 ml/mmHg) and colonic compliance (from 7.9 +/- 0.4 to 9 +/- 0.7 ml/mmHg) during stepwise distensions. Intensity of urge and pain perception during rectal distension was increased by neurotensin (P < 0.05). Sensations during colonic distensions were not altered by neurotensin. For colonic reflexes, during rectal distension the colonic bag volume increased significantly (P < 0.05), whereas during colonic distension rectal bag volume decreased significantly (P < 0.05). Neurotensin delayed the occurrence of these reflexes: they were present at significantly higher pressures compared to placebo (P < 0.05).

We demonstrated the presence of both a rectocolonic inhibitory and a colorectal stimulatory reflex in healthy volunteers. Neurotensin increases compliance and modulates rectal but not colonic sensitivity. Colorectal and rectocolonic reflexes are impaired during infusion of neurotensin.