Objective: To establishment and verify pelvic nerve denervation (PND) model in mice.
Methods: (1) Establishment of models. Seventy-two healthy male SPE class C57 mice with age of 7 weeks and body weight of (25±1) g were chosen. These 72 mice were randomly divided into PND group containing 36 mice and sham operation group containing 36 mice. Referring to the establishment method of PND rats, after anesthesia, a laparotomy was performed on the mouse with an abdominal median incision. Under the dissection microscope, the pelvic nerves behind and after each sides of the prostate gland were bluntly separated with cotton swabs and cut with a dissecting scissor. After the operation, the urination of mice was assisted twice every day. For the mice of sham operation group, the pelvic nerves were only exposed without cutting. (2) Detection of models. Colonic transit test was performed in 18 mice chosen randomly from each group to detect the colonic transit ratio (colored colon by methylene blue/ whole colon) and visceral sensitivity tests was performed in the rest mice to observe and record the changes of electromyogram.
Results: Three mice died of colonic transit test in each group. Uroschesis occurred in all the mice of PND group and needed bladder massage to assist the urination. Colonic transit test showed that the colonic transit ratios of sham operation group at postoperative day (POD) 1, 3 and 7 were (0.4950±0.3858)%, (0.6386±0.1293)% and (0.6470±0.1088)% without significant difference (F=0.3647, P=0.058), while in PND group, the colonic transit ratio at POD 7 [(0.6044±0.1768) %] was obviously higher than that both at POD 3[(0.3876±0.1364)%, P=0.022] and POD 1[(0.2542±0.0371)%, P=0.001], indicating a recovery trend of colonic transit function (F=9.143, P=0.004). Compared with the sham operation group, the colonic transit function in PND group decreased significantly at POD 1 and POD 3(both P<0.05), and at POD 7, there was no significant difference between two groups. Visceral sensitivity test showed that the visceral sensitivity of sham operation group at POD 1, 3 and 7 was 24.2808±9.5566, 33.6725±7.9548 and 43.9086±12.1875 with significant difference (F=5.722, P=0.014). The visceral sensitivity of PND group at POD 1, 3 and 7 was 11.7609±2.1049, 21.8415±8.1527 and 26.2310±4.2235 with significant difference as well (F=11.154, P=0.001). The visceral sensitivity at POD 3 and POD 7 was obviously higher than that at POD 1 (P=0.006, P<0.001), and there was no significant difference between POD 3 and POD 7 (P=0.183). Compared with sham operation group, the visceral sensitivity of PND group decreased significantly at POD 1, 3 and 7(all P<0.05).
Conclusions: Denervation of pelvic nerves can obviously decrease the colonic transit function and the visceral sensitivity of mice, but these changes can recover over time, which suggests that the establishment of PND model in mice is successful.