NMDA receptor mRNA expression in NOS-containing neurons in the spinal trigeminal nucleus of the rat.

The spinal trigeminal nucleus (STN) is involved in the transmission of orofacial sensory information. Nitric oxide (NO), an important neuromessenger, and the glutamate receptor subtype, NMDA NR1, have been implicated in nociception in the STN. However, the anatomical relationship of NO and NMDA NR1 has not been investigated within this nucleus. Using both immunocytochemical (against NO synthase; NOS) and in situ hybridization studies of NMDA NR1 receptor mRNA, we found that NOS-containing neurons in the STN expressed more mRNA for NR1 than did non-NOS-containing neurons in the STN. These data suggest that NMDA activation may lead to NO production in the STN and is consistent with previous studies, implicating both NMDA and NO in nociception.