Sj. Siegel et al., REGIONAL, CELLULAR, AND ULTRASTRUCTURAL DISTRIBUTION OF N-METHYL-D-ASPARTATE RECEPTOR SUBUNIT-1 IN MONKEY HIPPOCAMPUS, Proceedings of the National Academy of Sciences of the United Statesof America, 91(2), 1994, pp. 564-568
The regional, cellular, and subcellular distributions of N-methyl-D-as
partate (NMDA) receptor subunit 1, NMDAR-1, were investigated in monke
y hippocampus by using a monoclonal antibody directed against a fusion
protein corresponding to aa 660-811 of NMDAR-1. The data indicate tha
t many neurons in each subfield of the hippocampus contain NMDAR-1 pro
tein, although the intensity and distribution of immunoreactivity vari
ed across regions, strata, and cellular compartments. In stratum lucid
um of CA3, messy fiber axons were immunoreactive for NMDAR-1, which ma
y correspond to previously hypothesized presynaptic receptors. NMDAR-1
-labeled postsynaptic profiles were present in stratum radiatum of CA3
but were largely absent from stratum lucidum. Such intraneuronal segr
egation of glutamate receptor subunits or classes may be spatially cor
related with afferent systems that exhibit laminar segregation and ter
minate in different portions of the postsynaptic dendritic tree. For e
xample, in CA3 pyramidal cells, NMDA receptors are postsynaptic in dis
tal apical dendrites (stratum radiatum), where NMDA-dependent longterm
potentiation in rats is mediated by associational/commissural afferen
ts, and are absent from proximal apical dendrites (stratum lucidum), w
here NMDA-independent longterm potentiation is mediated by the messy f
iber input.