Presynaptic NMDA receptors in the neocortex are both auto- and heteroreceptors.
We used electron microscopic immunocytochemistry with antibodies against NR1 and NR2A and B subunits to study the distribution of N-methyl-D-aspartate (NMDA) receptors in presynaptic axon terminals in the rat cerebral cortex. In all sections examined, NR1 and NR2A/B immunoreactivities were observed in axon terminals: NR1- and NR2A/B-positive axon terminals made both symmetrical and asymmetrical synapses on unlabelled dendritic profiles. Combined pre- and postembedding studies showed that all NR1 and NR2A/B-positive axon terminals making symmetrical synapses were gamma-aminobutyric acid (GABA)-positive. These observations show that both auto- and hetero- NMDA receptors do exist in the cerebral cortex, and indicate that part of the effects of NMDA receptor activation might be determined by modulating glutamate and GABA release.
DeBiasi
S
S
Department of General Physiology and Biochemistry, University of Milan, Italy.
Minelli
A
A
Melone
M
M
Conti
F
F
D000818:Animals; D001369:Axons / Q000648:ultrastructure*; D002540:Cerebral Cortex / Q000648:ultrastructure*; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D017729:Presynaptic Terminals / Q000648:ultrastructure*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000648:ultrastructure*
D016194:Receptors, N-Methyl-D-Aspartate