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Adaptation to synaptic inactivity in hippocampal neurons
Tara C Thiagarajan1, Maria Lindskog, Richard W Tsien
1Department of Molecular and Cellular Physiology, Beckman Center, Stanford University School of Medicine, Stanford, California 94305, USA.
Neuron
|September 1, 2005
Summary
Activity deprivation in CNS neurons triggers adaptive synaptic changes. Prolonged AMPAR blockade reveals molecular mechanisms involving L-type Ca2+ channels and GluR1 homomers, leading to metaplasticity.
Area of Science:
- Neuroscience
- Synaptic Plasticity
- Molecular Basis of Neuronal Adaptation
Background:
- Central Nervous System (CNS) neurons exhibit adaptive modifications in synaptic transmission during activity deprivation.
- The molecular underpinnings of these slow adaptive changes remain largely unelucidated.
- Existing knowledge primarily focuses on rapid synaptic plasticity mechanisms.
Purpose of the Study:
- To investigate the molecular mechanisms driving adaptive synaptic modifications in response to prolonged activity deprivation.
- To identify key ion channels and receptor subunits involved in these homeostatic and metaplastic changes.
- To differentiate these adaptive changes from classical synaptic plasticity.
Main Methods:
- Utilized prolonged blockade of AMPA-type glutamate receptors (AMPARs) to induce activity deprivation in CNS neurons.
- Investigated the role of L-type Ca2+ channels in mediating adaptive synaptic changes.
- Analyzed changes in vesicle pool size, turnover rate, and postsynaptic receptor contribution, focusing on GluR1 homomers.
- Examined morphological synapse scaling and the contribution of Ca2+-permeable AMPARs.
Main Results:
- Prolonged AMPAR blockade led to a loss of Ca2+ entry via L-type Ca2+ channels.
- Observed an increase in vesicle pool size and turnover rate at synapses.
- Demonstrated a postsynaptic enhancement of GluR1 homomer contribution, particularly at larger synapses.
- Identified a shift towards synaptic drive mediated by Ca2+-permeable homomeric GluR1 receptors.
- Synaptic changes were consistent with morphological scaling and indicated profound metaplasticity.
Conclusions:
- Prolonged AMPAR blockade induces significant adaptive changes in synaptic transmission, extending beyond synaptic homeostasis.
- L-type Ca2+ channels and GluR1 homomers play critical roles in the molecular basis of these adaptive modifications.
- These findings suggest a form of metaplasticity, representing a deeper level of neuronal adaptation to activity deprivation.