Distribution, Density, and Clustering of Functional Glutamate Receptors Before and After Synaptogenesis in Hippocampal Neurons

• Published in: Journal of neurophysiology Vol. 84; no. 3; pp. 1573 - 1587
• Main Authors: Cottrell, Jeffrey R, Dube, Gilles R, Egles, Christophe, Liu, Guosong
• Format: Journal Article
• Language: English
• Published: United States Am Phys Soc 01-09-2000
• Subjects: Animals; Animals, Newborn; Cell Differentiation - physiology; Cells, Cultured; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists - pharmacology; Fluorescent Dyes; Glutamic Acid - administration & dosage; Glutamic Acid - metabolism; Hippocampus - metabolism; Hippocampus - ultrastructure; Ion Channel Gating - drug effects; Iontophoresis; Membrane Potentials - drug effects; Membrane Potentials - physiology; Mice; Neurons - metabolism; Neurons - ultrastructure; Patch-Clamp Techniques; Pyridinium Compounds; Quaternary Ammonium Compounds; Rats; Receptor Aggregation - drug effects; Receptor Aggregation - physiology; receptor clustering; Receptors, AMPA - metabolism; Receptors, AMPA - ultrastructure; Receptors, Glutamate - metabolism; Receptors, Glutamate - ultrastructure; Receptors, N-Methyl-D-Aspartate - metabolism; Receptors, N-Methyl-D-Aspartate - ultrastructure; Synapses - metabolism; Synapses - ultrastructure
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.2000.84.3.1573

RIKEN-MIT Neuroscience Research Center, Center for Learning and
Memory, Department of Brain and Cognitive Sciences, and Department of
Biology, Massachusetts Institute of Technology, Cambridge,
Massachusetts 02139
Cottrell, Jeffrey R.,
Gilles R. Dubé,
Christophe Egles, and
Guosong Liu.
Distribution, Density, and Clustering of Functional Glutamate
Receptors Before and After Synaptogenesis in Hippocampal Neurons. J. Neurophysiol. 84: 1573-1587, 2000. Postsynaptic differentiation during glutamatergic synapse formation is
poorly understood. Using a novel biophysical approach, we have
investigated the distribution and density of functional glutamate
receptors and characterized their clustering during synaptogenesis in
cultured hippocampal neurons. We found that functional
-amino-3-hydroxy-5-methyl-4-isoxazolpropionate (AMPA) and
N -methyl- D -aspartate (NMDA) receptors are evenly
distributed in the dendritic membrane before synaptogenesis with an
estimated density of 3 receptors/µm 2 . Following
synaptogenesis, functional AMPA and NMDA receptors are clustered at
synapses with a density estimated to be on the order of
10 4 receptors/µm 2 , which
corresponds to ~400 receptors/synapse. Meanwhile there is no
reduction in the extrasynaptic receptor density, which indicates that
the aggregation of the existing pool of receptors is not the primary
mechanism of glutamate receptor clustering. Furthermore our data
suggest that the ratio of AMPA to NMDA receptor density may be
regulated to be close to one in all dendritic locations. We also
demonstrate that synaptic AMPA and NMDA receptor clusters form with a
similar time course during synaptogenesis and that functional AMPA
receptors cluster independently of activity and glutamate receptor
activation, including following the deletion of the NMDA receptor NR1
subunit. Thus glutamate receptor activation is not necessary for the
insertion, clustering, and activation of functional AMPA receptors
during synapse formation, and this process is likely controlled by an
activity-independent signal.