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Differential regulation of dendrite complexity by AMPA receptor subunits GluR1 and GluR2 in motor neurons
Author(s) -
Prithviraj Ranjini,
Kelly Kristen M.,
EspinozaLewis Ramon,
Hexom Tia,
Clark Amy B.,
Inglis Fiona M.
Publication year - 2007
Publication title -
developmental neurobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.716
H-Index - 129
eISSN - 1932-846X
pISSN - 1932-8451
DOI - 10.1002/dneu.20590
Subject(s) - ampa receptor , dendrite (mathematics) , biology , synaptogenesis , filopodia , neuroscience , dendritic filopodia , glutamate receptor , motor neuron , dendritic spine , microbiology and biotechnology , synaptic plasticity , excitatory postsynaptic potential , receptor , hippocampal formation , spinal cord , inhibitory postsynaptic potential , genetics , actin , geometry , mathematics
Activity‐dependent developmental mechanisms in many regions of the central nervous system are thought to be responsible for shaping dendritic architecture and connectivity, although the molecular mechanisms underlying these events remain obscure. Since AMPA glutamate receptors are developmentally regulated in spinal motor neurons, we have investigated the role of activation of AMPA receptors in dendritic outgrowth of spinal motor neurons by overexpression of two subunits, GluR1 and GluR2, and find that dendrite outgrowth is differentially controlled by expression of these subunits. Overexpression of GluR1 was associated with greater numbers of filopodia, and an increase in the length and complexity of dendritic arbor. In contrast, GluR2 expression did not alter dendritic complexity, but was associated with a moderate increase in length of arbor, and decreased numbers of filopodia. Neither GluR1 nor GluR2 had any effect on the motility of filopodia. In addition, GluR1 but not GluR2 expression increased the density of dendritic puncta incorporating a GFP‐labeled PSD95, suggesting that GluR1 may mediate its effect in part by augmenting the number of excitatory synapses within motor neuron dendrites. Together these results suggest that in spinal motor neurons, AMPA receptors composed of GluR1 subunits may facilitate neurotrophic mechanisms in these neurons, permitting sustained dendrite outgrowth and synaptogenesis, whereas expression of AMPA receptors containing GluR2 acts to preserve existing dendritic arbor. Thus, the observed downregulation of GluR1 in motor neurons during postnatal development may limit the formation of new dendrite segments and synapses, promoting stabilized synaptic connectivity. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2008