ABSTRACT
In this study histochemical method was used. It has been found that on the seventh day after epidural administration of capsaicin substance p like immuno- reactivity (SPAR) in laminae Ⅰ-Ⅱ of dorsal horn of spinal cord decreased obv- iously as compared with that of vehicle treated animals, meanwhile, the activity of fluoride resistant acid phosphatase (FRAP) in both laminae Ⅱ of dorsal horn of spinal cord and the B-type cells of spinal ganglion disappeared. On the cont- rary the Leu-enkephalin immunoreactivity (ENK-IR) in laminae Ⅰ-Ⅲ of dorsal horn of spinal cord apparently increased as compared with that in vehicle group. the evidence from functional measurement showed that capsaicin can raise pain threshold, however, vehicle didnot have obvious influence on pain threshold. The foregoing results suggest that epidural administration of capsaicin in adult rat can effect the level of neurontransmitters, the activity of enzymes and block the con- duction of the primary afferent C fibers; the capsaicin-sensitive C fibers may have relationship with the ENK-containing interneurons in dorsal horn of spinal cord.