Decreased expression of N-methyl-D-aspartate (NMDA) receptors in rat dorsal root ganglion following complete Freund's adjuvant-induced inflammation: an immunocytochemical study for NMDA NR1 subunit

The changes in expression of NMDA NR1, an essential functional subunit of N -methyl-D-aspartate (NMDA) receptors, were examined in the rat lumbar dorsa l root ganglion (DRG) by immunocytochemical technique following injection o f complete Freund's adjuvant (CFA) into the unilateral hindpaw. The results showed that there appeared a significant and several days-lasting down-reg ulation in expression of NMDA NR1 in the lumbar DRG following CFA injection , and especially, this change mainly appeared in the small and medium sized DRG neurons. It is suggested that a long-lasting flow of nociceptive input s in nociceptors will elicit a decreased expression of NMDA receptors on pr imary afferent neurons and this plastic change would act as a factor leadin g towards the hyposensitization for nociception at the nociceptor level. (C ) 1999 Published by Elsevier Science Ireland Ltd. All rights reserved.