Different expressions of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid and N-methyl-D-aspartate receptor subunit mRNAs between visceromotor and somatomotor neurons of the rat lumbosacral spinal cord

The glutamatergic transmission system plays a key role in afferent and effe rent pathways involved in micturition. By in situ hybridization combined wi th retrograde Fast Blue labeling, expression of alpha-amino-3-hydroxy-5-met hyl-4-isoxazole propionic acid (AMPA) receptor (GluR-A to -D) and N-methyl- D-aspartate (NMDA) receptor (NR1 and NR2A-D) subunit mRNAs were examined in visceromotor and somatomotor neurons of the rat lumbosacral spinal cord. P arasympathetic preganglionic neurons (PC;Ns) in the intermediolateral nucle us highly expressed GluR-A and GluR-B subunit mRNAs, with very low levels f or GluR-C and GluR-D subunits. As for the NMDA receptor, PGNs were associat ed with abundant signals for NR1 subunit mRNA, but without any NR2 subunit mRNAs. On the other hand, somatomotor neurons in the ventral horn (dorsolat eral nucleus) express all four AMPA receptor subunit mRNAs, showing relativ ely abundant expressions of GluR-C and GluR-D subunit mRNA compared with PG Ns. In addition to high levels of NR1 subunit mRNA, dorsolateral nucleus ne urons moderately expressed NR2A and NR2B subunit mRNAs. These results sugge st that molecular organization of both AMPA and NMDA receptor channels are distinct between PGNs and dorsolateral nucleus neurons. Considering that na tive NMDA receptors are heteromeric channels composed of NR1 and NR2 subuni ts, it seems Likely that dorsolateral nucleus neurons, not PGNs, are provid ed with functional NMDA receptors, which could induce activity-dependent ch anges in synaptic transmission in the efferent pathway for the lower urinar y tract. (C) 1999 Wiley-Liss, Inc.