Alterations of substance P immunoreactivity in lumbar and thoracic segments of rat spinal cord in ultraviolet irradiation induced hyperalgesia of the hindpaw.

Substance P immunostaining was quantified on sections from the 4th-5th lumbar and midthoracic spinal segments of rats at the peak of hyperalgesia following ultraviolet irradiation-induced inflammation of one hindpaw. The area of the immunostaining in the lumbar dorsal horn was significantly decreased on both sides by 50%, while in the thoracic spinal cord, it was increased by 18% on the contralateral and stayed unchanged on the ipsilateral side.