Overexpression of TRPV1 after periphery nerve injury attenuates nerve regeneration in rats

Abstract

Objective: To observe the effect of the expressive or functional blockage of TRPV1 on nerve regeneration after sciatic trans-section injury. Methods: AMG-517, a kind of TRPV1 inhibitor, was injected into the surrounding area of the ipsilateral lumbar dorsal root ganglia while unilateral sciatic nerve was transected. A total of 24 healthy male Sprague-Dawley rats were divided into 4 groups: control group, injury only group, injury+ AMG-517 150 μg/kg group, injury+ AMG-517 300 μg/kg group. The injury only group was injected the same volume of medium. The release of CGRP from dorsal-horn of spinal cord, the number of axons at proximal stem of sciatic nerve after transection, and the expression of TRPV1 in dorsal root ganglion were detected using the methods of ELISA, Western blot and semi-thin section (1 μm)- toluidine blue staining 2 weeks after injury. Results: The release of CGRP in lumbar spinal dorsal horn was obviously decreased after AMG-517 treatment, which was the evidence of TRPV1 functional inhibition. CGRP in the control group was 0.15 ng/g, the injury only group 0.17 ng/g, AMG-517 150 μg/kg group 0.09 ng/g, and AMG-517 300 μg/kg group 0.11 ng/g(P<0.01). The number of axons which were myelinated or unmyelinated increased after the TRPV1 was inhibited by AMG-517(P<0.01). In addition, the injection of AMG-517 into surrounding dorsal root ganglion decreased the expression of TRPV1 in dorsal root ganglion(P<0.01). Conclusions: Over expression or activation of TRPV1 after periphery nerve injury has negative effect on nerve regeneration in fact; Inhibiting the over-expression or over-activation of TRPV1 after nerve injury facilitates axonal regeneration and nerve repair.