Effect of retrograde colonic electrical stimulation on colonic transit and stress-induced visceral hypersensitivity in rats with irritable bowel syndrome

Objective: To evaluate the effects of retrograde colonic electrical stimulation (RCES) with trains of short pulses and RCES with long pulses on colonic transit in irritable bowel syndrome (IBS) rats and to investigate whether stress-induced visceral hypersensitivity could be alleviated by RCES so as to find a valuable new approach for IBS treatment. Methods: A total of 48 male rats were randomly divided into model group and control group. Visceral hypersensitivity model was induced by a 6-day HIS protocol composed of two stressors, restraint stress for 40 min and forced swimming stress for 20 min. The extent of visceral hypersensitivity was quantified by electromyography and abdominal withdrawal reflx scores (AWRs) of colorectal distension (use a balloon) at different pressures. After the modeling, all rats were equipped with electrodes in descending colon for retrograde electrical stimulation and a PE tube for perfusing phenol red saline solution in the ileocecus. After recovering from surgery, RCES with long pulses. RCES with trains of short pulses, and sham RCES were performed in colonic serosa of rats for 40 min in six groups of 8 each, including three groups of visceral hypersensitivity rats and three groups of health rats. Colonic transit was assessed by calculating the output of phenol red from the anus every 10 min for 90 min. Finally, the extent of visceral hypersensitivity will be quantified again in model group. Results: After the 6-day HIS protocol, the HIS rats displayed an increased sensitivity to colorectal distention, compared to control group at different distention pressures (P<0.01). CRES with trains of short pulses and long pulses significantly attenuated the hypersensitive responses to colorectal distention in the HIS rats compared with sham RCES group (P<0.01). The effects of RCES on rats colon transmission: In the IBS rats, the colonic emptying were (77.4 +/- 3.4)%, (74.8 +/- 2.4)% and (64.2 +/- 1.6)% in the sham RCES group, long pulses group and trains of short pulses group at 90 min; In healthy rats, The colonic emptying was (65.2 +/- 3.5)%, (63.5 +/- 4.0)% and (54.0 +/- 2.5)% in the sham RCES group, long pulses group and trains of short pulses group at 90 min. Conclusion: RCES with long pulses and RCES with trains of short pulses can significantly alleviate stress-induced visceral hypersensitivity. RCES with trains of short pulses has an inhibitory effect of colonic transit, both in visceral hypersensitivity rats and healthy rats.