PT  - JOURNAL ARTICLE
AU  - Miklós Antal
AU  - Yugo Fukazawa
AU  - Mária Eördögh
AU  - Dóra Muszil
AU  - Elek Molnár
AU  - Makoto Itakura
AU  - Masami Takahashi
AU  - Ryuichi Shigemoto
TI  - Numbers, Densities, and Colocalization of AMPA- and NMDA-Type Glutamate Receptors at Individual Synapses in the Superficial Spinal Dorsal Horn of Rats
AID  - 10.1523/JNEUROSCI.1551-08.2008
DP  - 2008 Sep 24
TA  - The Journal of Neuroscience
PG  - 9692--9701
VI  - 28
IP  - 39
4099  - http://www.jneurosci.org/content/28/39/9692.short
4100  - http://www.jneurosci.org/content/28/39/9692.full
SO  - J. Neurosci.2008 Sep 24; 28
AB  - Ionotropic glutamate receptors play important roles in spinal processing of nociceptive sensory signals and induction of central sensitization in chronic pain. Here we applied highly sensitive freeze-fracture replica labeling to laminae I–II of the spinal dorsal horn of rats and investigated the numbers, densities, and colocalization of AMPA- and NMDA-type glutamate receptors at individual postsynaptic membrane specializations with a high resolution. All glutamatergic postsynaptic membranes in laminae I–II expressed AMPA receptors, and most of them (96%) were also immunoreactive for the NR1 subunit of NMDA receptors. The numbers of gold particles for AMPA and NMDA receptors at individual postsynaptic membranes showed a linear correlation with the size of postsynaptic membrane specializations and varied in the range of 8–214 and 5–232 with median values of 37 and 28, whereas their densities varied in the range of 325–3365/μm2 and 102–2263/μm2 with median values of 1115/μm2 and 777/μm2, respectively. Virtually all (99%) glutamatergic postsynaptic membranes expressed GluR2, and most of them (87%) were also immunoreactive for GluR1. The numbers of gold particles for pan-AMPA, NR1, and GluR2 subunits showed a linear correlation with the size of postsynaptic surface areas. Concerning GluR1, there may be two populations of synapses with high and low GluR1 densities. In synapses larger than 0.1 μm2, GluR1 subunits were recovered in very low numbers. Differential expression of GluR1 and GluR2 subunits suggests regulation of AMPA receptor subunit composition by presynaptic mechanism.