Published online Aug 21, 2014. doi: 10.3748/wjg.v20.i31.10886
Revised: April 25, 2014
Accepted: July 22, 2014
Published online: August 21, 2014
AIM: To investigate whether cold water intake into the stomach affects colonic motility and the involvement of the oxytocin-oxytocin receptor pathway in rats.
METHODS: Female Sprague Dawley rats were used and some of them were ovariectomized. The rats were subjected to gastric instillation with cold (0-4 °C, cold group) or room temperature (20-25 °C, control group) saline for 14 consecutive days. Colon transit was determined with a bead inserted into the colon. Colonic longitudinal muscle strips were prepared to investigate the response to oxytocin in vitro. Plasma concentration of oxytocin was detected by ELISA. Oxytocin receptor expression was investigated by Western blot analysis. Immunohistochemistry was used to locate oxytocin receptors.
RESULTS: Colon transit was slower in the cold group than in the control group (P < 0.05). Colonic smooth muscle contractile response to oxytocin decreased, and the inhibitory effect of oxytocin on muscle contractility was enhanced by cold water intake (0.69 ± 0.08 vs 0.88 ± 0.16, P < 0.05). Atosiban and tetrodotoxin inhibited the effect of oxytocin on colonic motility. Oxytocin receptors were located in the myenteric plexus, and their expression was up-regulated in the cold group (P < 0.05). Cold water intake increased blood concentration of oxytocin, but this effect was attenuated in ovariectomized rats (286.99 ± 83.72 pg/mL vs 100.56 ± 92.71 pg/mL, P < 0.05). However, in ovariectomized rats, estradiol treatment increased blood oxytocin, and the response of colonic muscle strips to oxytocin was attenuated.
CONCLUSION: Cold water intake inhibits colonic motility partially through oxytocin-oxytocin receptor signaling in the myenteric nervous system pathway, which is estrogen dependent.
Core tip: Colon transit was decreased and oxytocin-induced inhibition of colonic contraction was enhanced in rats with cold water intake. Atosiban and tetrodotoxin inhibited the effect of oxytocin on colonic motility. Cold water intake increased blood concentration of oxytocin and expression of oxytocin receptors in colon. Estradiol regulated blood concentration of oxytocin and oxytocin-induced colonic contraction. The results suggested that cold water intake inhibited colonic motility through oxytocin-oxytocin receptor signaling in the myenteric nervous system pathway, which is estrogen dependent. The estradiol-oxytocin-oxytocin receptor-colonic contractile pathway might be a new therapeutic target for irritable bowel syndrome in females.