[Experimental study on reconstruction of physiological reflex arc after medullary cone injury in rats]

To establish the animal model of the artificial physiological reflex arc with the reconstruction of the sensory and the motorial functions of atonic bladder simultaneously in the rats, and to provide the foundation to further investigate the repairing effectiveness of this technique.

There were 20 adult male SD rats (weighing 280-300 g) which were randomly divided into 2 groups (n = 10): group A and group B. Group A was anastomosis of the ventral roots (VR) and the dorsal roots (DR) between L6 and S2 simultaneously to establish the model of the artificial physiological reflex arc. Group B was anastomosis of the main trunk between L6 and S2 to establish the model. The contents of the observation included: (1) To measure the external diameter of the VR, DR and the main trunk of L6 and S2 with the sliding caliper; and to measure not only the distance between L6 and S2 but also the separable length of L6 with the ruler. (2) Fast Blue dyeing of the VR, DR and the main trunk of L6 and S2 was performed to count their nerve fibers assisted by the Leica FW4000 system 2 weeks after opertation. (3) The observation of the urination of the rat and BBB scoring to evaluate the motorial function of the lower limbs was performed postoperatively.

(1) L6 located in the lateral side of the S1-4 in the vertebral body of L6. The external diameters of the VR, DR and the main trunk of L6 were (0.68 +/- 0.13), (0.88 +/- 0.10) and (1.54 +/- 0.33) mm, respectively, while those of S2 were (0.62 +/- 0.08), (0.79 +/- 0.14) and (1.39 +/- 0.42) mm, respectively. The distance between L6 and S2 was (14.21 +/- 1.95) mm, and the separable length of L6 was (10.76 +/- 2.11) mm. Furthermore, the microdissection indicated the VR and the DR between L6 and S2 could be anastomosed respectively with no-tension at the level of the vertebral body of L6; and the main trunk of L6 and S2 could be anastomosed with no-tension at the level of the confluens of L5,6. (2) With Fast Blue dyeing, there were 892 +/- 32, 354 +/- 26 and 532 +/- 17 nerve fibers of the VR, DR and the main trunk of L6, respectively. And there were 788 +/- 29, 325 +/- 19, and 478 +/- 22 nerve fibers of the VR, DR and the main trunk of S2, respectively. There were no volar ulcer, trichomadesis and self-eating of the affected limbs in the both groups postoperatively. The urinations of the rats after operation were not different from those before operation. The mean BBB scores of pre- and postoperation in group A were 20.20 +/- 0.35 and 19.80 +/- 0.23, respectively; the mean BBB scores of pre- and postoperation in group B were 20.20 +/- 0.35 and 19.20 +/- 0.31, respectively. There was no significant difference of the above indexes between group A and group B (P > 0.05).

Anastomosis of the VR and the DR between L6 and S2 simultaneously in rats is an ideal animal model to establish the artificial physiological reflex arc owing to its simple and reproducible procedures.