Effects of intravesical capsaicin on the substance P- and CGRP-immunoreactive terminals of the rat spinal dorsal horn / 대한해부학회지

ABSTRACT

Visceral afferent nerve fibers containing substance P or calcitonin gene-related peptide (CGRP) are distributed in the bladder wall, and are known to be stimulated by and then desensitized by capsaicin. Recently, there have been some reports on the effectiveness of intravesical capsaicin administration for the treatment of hypersensitive lower urinary tract disorder or neurogenic bladder. In this study, the effects of intravesical capsaicin on the substance P or CGRP immunoreactivities in the spinal dorsal horn were investigated and the mechanism of capsaicin treatment for bladder disorders was revealed. After intravesical administration of capsaicin, the substance P and CGRP immunoreactive areas were measured at the dorsal horn of L4 and S1 spinal cord. Before capsaicin treatment, the substance P immuno- reactive area was 2.61+/-0.78 x 105 mm2 in L4 and 1.66+/-0.49 x 105 mm2 in S1. The substance P immunoreactivity was markedly reduced 1~2 weeks after capsaicin treatment in both L4 and S1 spinal cord. The CGRP immunoreactive area was 1.74+/-0.52 x 105 mm2 in L4 and 1.14+/-0.69 x 105 mm2 in S1, but was not reduced after capsaicin treatment. Therefore, capsaicin administered intravesically desensitizes nerve fibers containing substance P and consequently suppresses pain and voiding reflex.