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Updated: Jun 25, 2026
Two-photon Calcium Imaging in Neuronal Dendrites in Brain Slices
Published on: March 15, 2018
Role of Ca2+/calmodulin-dependent protein kinase II in dendritic spine remodeling during epileptiform activity in
Xiang-ming Zha1, Michael E Dailey, Steven H Green
1Department of Biology, University of Iowa, Iowa City, IA 52242-1324, USA.
Abstract:
Epileptiform activity (EA) in vivo and in vitro induces a loss of dendritic spines and synapses. Because CaMKII has been implicated in synaptogenesis and synaptic plasticity, we investigated the role of CaMKII in the effects of EA on spines, using rat hippocampal slice cultures. To visualize dendrites and postsynaptic densities (PSDs) in pyramidal neurons in the slices, we used biolistic transfection to express either free GFP or a PSD95-YFP construct that specifically labels PSDs. This allowed us to distinguish two classes of dendritic protrusions: spines that contain PSDs, and filopodia that lack PSDs and that are, on average, longer than spines. By these criteria, 48 hr of EA caused a decrease specifically in the number of spines. Immunoblots showed that EA increased CaMKII activity in the slices. Inhibition of CaMKII by expression of AIP, a specific peptide inhibitor of CaMKII, reduced spine number under basal conditions and failed to prevent EA-induced spine loss. However, under EA conditions, AIP increased the number of filopodia and the number of PSDs on the dendritic shaft. These data show at least two roles for CaMKII activity in maintenance and remodeling of dendritic spines under basal or EA conditions. First, CaMKII activity promotes the maintenance of spines and spine PSDs. Second, CaMKII activity suppresses EA-induced formation of filopodia and suppresses an increase in shaft PSDs, apparently by promoting translocation of PSDs from dendritic shafts to spines and/or selectively stabilizing spine rather than shaft PSDs.
Insights
Epileptiform activity (EA) causes loss of dendritic spines. Calcium-calmodulin dependent protein kinase II (CaMKII) activity is crucial for maintaining spines and preventing filopodia formation during EA.
Area of Science:
- Neuroscience
- Cell Biology
- Synaptic Plasticity
Background:
- Epileptiform activity (EA) is known to cause loss of dendritic spines and synapses.
- Calcium-calmodulin dependent protein kinase II (CaMKII) plays a role in synaptogenesis and synaptic plasticity.
Purpose of the Study:
- Investigate the role of CaMKII in the effects of EA on dendritic spines.
- Differentiate between spines and filopodia and their response to EA and CaMKII inhibition.
Main Methods:
- Used rat hippocampal slice cultures.
- Expressed free GFP or PSD95-YFP in pyramidal neurons to visualize dendritic structures.
- Induced EA and inhibited CaMKII using AIP peptide inhibitor.
- Analyzed spine and filopodia numbers and PSD localization.
Main Results:
- EA decreased the number of dendritic spines but not filopodia.
- EA increased CaMKII activity.
- CaMKII inhibition reduced basal spine number and increased filopodia and shaft PSDs under EA conditions.
- CaMKII inhibition did not prevent EA-induced spine loss but altered other dendritic structures.
Conclusions:
- CaMKII activity is essential for maintaining dendritic spines and their postsynaptic densities (PSDs).
- CaMKII activity suppresses EA-induced filopodia formation and PSDs on dendritic shafts.
- CaMKII may promote PSD translocation to spines or stabilize spine PSDs over shaft PSDs.
