Objective: To evaluate the effects and mechanism of colonic electrical stimulation (CES) on colonic transit.
Methods: 76 male SD rats were equipped with colonic electrodes for stimulation and a catheter in the colon and then randomly divided onto 6 groups: normal saline-(NS)/CES group (14 rats), NS-non-CES group (14 rats), N-nitro-L-arginine (L-NNA)/CES group (12 rats), L-NNA/non-CES group (12 rats), atropine/CES group (12 rats), and atropine/non-CES group (12 rats). All rats underwent intraperitoneal injection of NS, L-NNA, nitric oxide synthesis blocker, or atropine before colon transit. Colonic transit was assessed by calculating the output of phenol red from the anus every 10 min for 90 min CES with trains of short-pulses was performed during the first 40 min of the transit test in the 3 CES groups.
Results: (1) CES significantly enhanced the colonic transit. The colonic emptying rate 90 min after the injection of phenol red of the NS/CES group was 82% +/- 5%, significantly higher than that of the NS/non-CES group (57% +/- 6%, P = 0.002) with a 43% increase. (2) L-NNA delayed the colonic transit and prevented the accelerative effect of CES on colonic transit. (3) The phenol red emptying rate 90 min after the injection of the atropine/non-CES group was 16% +/- 3%, significantly lower than that of the NS/non-CES group (P < 0.001). The phenol red emptying rate 90 min after the injection of the atropine/CES group was 41% +/- 6%, significantly higher than that of the atropine/non-CES group (16% +/- 3%, P = 0.01).
Conclusion: CES has an excitatory effect on colonic transit and this excitatory effect may be mediated via the nitrergic pathway, not the cholinergic pathway.