N-methyl-D-aspartate receptor 1 in the caudate-putamen nucleus: ultrastructural localization and co-expression with sorcin, a 22,000 mol. wt calcium binding protein.
Entry of calcium through N-methyl-D-aspartate-type glutamate receptors in the caudate-putamen nucleus is essential for normal motor activity, but can produce cytotoxicity with continued stimulation and subsequent release of intracellular calcium. To determine potential functional sites for N-methyl-D-aspartate receptor activation in this region, we examined the ultrastructural localization of the R1 subunit of the N-methyl-D-aspartate receptor (NMDAR1) in rat brain. In addition, we comparatively examined the localization of NMDAR1 and sorcin, a 22,000 mol. wt calcium binding protein present in certain striatal neurons and involved in calcium-induced calcium release. NMDAR1-like immunoreactivity was seen at synaptic and non-synaptic sites on neuronal plasma membranes. Of 1514 NMDAR1-labeled profiles, 62% were dendrites and dendritic spines and the remainder were mainly unmyelinated axons and axon terminals. Sorcin-like immunoreactivity was present in 39% of the profiles that contained NMDAR1 labeling, most (533/595) of which were dendrites and dendritic spines. Of 1807 sorcin-labeled profiles, 42% were identified, however, as small processes including spine necks and unmyelinated axons or axon terminals. These profiles also occasionally contained NMDAR1 or showed synaptic or appositional contacts with other NMDAR1-immunoreactive neurons. The results of this study suggest that in the caudate-putamen nucleus, activation of NMDA receptors permits calcium influx at plasmalemmal sites mainly on dendrites where sorcin may play a role in calcium-induced calcium release. The presence of sorcin in some, but not all NMDA-containing neurons in the caudate-putamen nucleus has potential implications for the known differential vulnerability of certain striatal neurons to excitotoxins.
Gracy
K N
KN
Department of Neurology and Neuroscience, Cornell University Medical College, New York, NY 10021, USA.
Clarke
C L
CL
Meyers
M B
MB
Pickel
V M
VM
D000818:Animals; D001369:Axons / Q000737:chemistry; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D002421:Caudate Nucleus / Q000378:metabolism* / Q000648:ultrastructure; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D003712:Dendrites / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D005786:Gene Expression Regulation; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry; D017136:Ion Transport; D008297:Male; D016253:Microscopy, Immunoelectron; D008970:Molecular Weight; D009411:Nerve Endings / Q000737:chemistry; D009419:Nerve Tissue Proteins / Q000032:analysis* / Q000096:biosynthesis / Q000235:genetics; D011699:Putamen / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000032:analysis* / Q000096:biosynthesis / Q000235:genetics
D002118:Calcium; D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D009419:Nerve Tissue Proteins; D016194:Receptors, N-Methyl-D-Aspartate