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Impaired Regulation of Synaptic Strength in Hippocampal Neurons from GluR1‐Deficient Mice
Author(s) -
Andrásfalvy Bertalan K.,
Smith Mark A.,
Borchardt Thilo,
Sprengel Rolf,
Magee Jeffrey C.
Publication year - 2003
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2003.045575
Subject(s) - metaplasticity , synaptic scaling , synaptic plasticity , ampa receptor , neuroscience , synaptic fatigue , long term potentiation , synaptic augmentation , glutamate receptor , long term depression , nonsynaptic plasticity , silent synapse , hippocampal formation , biology , homeostatic plasticity , receptor , chemistry , biochemistry
Neurons of the central nervous system (CNS) exhibit a variety of forms of synaptic plasticity, including associative long‐term potentiation and depression (LTP/D), homeostatic activity‐dependent scaling and distance‐dependent scaling. Regulation of synaptic neurotransmitter receptors is currently thought to be a common mechanism amongst many of these forms of plasticity. In fact, glutamate receptor 1 (GluR1 or GluRA) subunits containing L‐α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate (AMPA) receptors have been shown to be required for several forms of hippocampal LTP and a particular hippocampal‐dependent learning task. Because of this importance in associative plasticity, we sought to examine the role of these receptors in other forms of synaptic plasticity in the hippocampus. To do so, we recorded from the apical dendrites of hippocampal CA1 pyramidal neurons in mice lacking the GluR1 subunit (GluR1 −/−). Here we report data from outside‐out patches that indicate GluR1‐containing receptors are essential to the extrasynaptic population of AMPA receptors, as this pool was nearly empty in the GluR1 −/− mice. Additionally, these receptors appear to be a significant component of the synaptic glutamate receptor pool because the amplitude of spontaneous synaptic currents recorded at the site of input and synaptic AMPA receptor currents evoked by focal glutamate uncaging were both substantially reduced in these mice. Interestingly, the impact on synaptic weight was greatest at distant synapses such that the normal distance‐dependent synaptic scaling used by these cells to counter dendritic attenuation was lacking in GluR1 −/− mice. Together the data suggest that the highly regulated movement of GluR1‐containing AMPA receptors between extrasynaptic and synaptic receptor pools is critically involved in establishing two functionally diverse forms of synaptic plasticity: LTP and distance‐dependent scaling.