NMDA receptors mediating Fos expression in rat spinal cord induced by subcutaneous injection of formalin.
AIM
To examine the effects of N-methyl-D-aspartate (NMDA) and non-NMDA receptors on noxious stimulation-induced Fos expression in the rat spinal cord.


METHODS
Formalin (2%) was injected s.c. into one hindpaw of the rat. Fos expression was exhibited by immunocytochemical technique.


RESULTS
Two hours after s.c. formalin, Fos-like immunoreactive (FLI) neurons were distributed mainly in medial part of the lamina I and the outer lamina II of the ipsilateral dorsal horn. dl-2-Amino-5-phosphonovalerate (APV) administered intrathecally (10 microL, 0.01, 0.1, or 1 g.L-1) before injection of formalin into a hindpaw reduced the number of FLI neurons dose-dependently in the dorsal horn (P < 0.01), while 6,7-dinitroquinoxaline-2, 3(1H,4H)-dione (DNQX) (1 g.L-1) was ineffective.


CONCLUSION
NMDA receptor mediated noxious stimulation-induced Fos expression in the rat spinal cord.