Changes of NOS activity in dorsal horn of spinal cord during formalininduced inflammatory pain and hyperalgesia in rats

Using NADPH d histochemistory, we observed the changes of nitric oxide synthase (NOS), especially in its time course, in the dorsal horn of the spinal cord during formalin induced inflammatory pain and hyperalgesia. The results showed that compared with control group ,there were increases in the number and staining degree of NADPH d positive cells in laminae Ⅰ～Ⅲ of the dorsal horn in 12 h,24 h and 48 h after formalin injection ,but the most obvious increase was in 24 h.The results indicate that during inflammatory pain and hyperalgesia, NOS activity in rat dorsal horn of the spinal horn is increased, and this increase is in a certain time course.