Exp Neurobiol 5:115-126, 1996

Capsaicin Induced Changes on the Substance P and CGRP Immunoreactive Nerve Cell Numbers and Sizes in the Dorsal Root Ganglion of the Rat

Won Taek Lee, Ho Yoon, Heung Dong Kim*, Kyung Ah Park

Department of Anatomy, Yonsei University College of Medicine, Seoul, 120-752, Korea
*Department of Pediatrics, Sanggye Paik Hospital, Inje University, 210 Sanggye-Dong Nowon-Ku, Seoul, Korea

The effect of capsaicin, the pungent ingredient in a wide variety of red peppers of the genus Capsicum, administration to the neonatal rat results in life-long insensitivity to the noxious stimuli accompanied by destruction of unmyelinated and lightly myelinated fibers, as well as small B-type dorsal root ganglion (DRG) neurons. The purpose of this study was to investigate the differential effects of capsaicin on the substance P (SP)- and calcitonin gene-related peptide (CGRP) immunoreactive sensory ganglion cells.

Twenty Sprague-Dawley rats (200-300 gm) pretreated with capsaicin (50 mg/kg) on the 1st and 2nd postnatal days were used for this study. L3 and T10 spinal ganglia were obtained and processed for the immunohistochemical methods. After single or double-labeling immunohistochemical staining against SP and CGRP antibodies, the L3 and T10 ganglion neuronal somata were counted and measured by computer-assisted image analyzer.

The numbers of the SP- and CGRP immunolabeled cells were reduced, especially the cells immunolabeled with both SP and CGRP. The area distribution of the T10 DRG cells pretreated with capsaicin were similar to those of the control rats, but large cells were observed much more than smaller neurons in the L3 DRG.

Key words: capsaicin, dorsal root ganglion, CGRP, substance P, pain