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Action potential timing determines dendritic calcium during striatal up-states
Jason N D Kerr1, Dietmar Plenz
1Unit of Neural Network Physiology, Laboratory of Systems Neuroscience, National Institute of Mental Health, Bethesda, Maryland 20892, USA. jason@mpinf-heidelberg.mps.edu.
Summary
Action potential timing during striatal up-states controls dendritic calcium levels, a process dependent on NMDA receptor activity. This finding is crucial for understanding synaptic plasticity in the corticostriatal pathway.
Area of Science:
- Neuroscience
- Cellular Neuroscience
- Synaptic Plasticity
Background:
- Up-states are critical for synaptic integration in the cortex and striatum.
- Striatal spiny projection neurons exhibit delayed action potential generation during up-states.
Purpose of the Study:
- To investigate the relationship between action potential timing and intracellular calcium ([Ca2+]i) transients during striatal up-states.
- To determine the role of NMDA receptors in regulating [Ca2+]i dynamics during up-states.
Main Methods:
- Studied somatic and dendritic [Ca2+]i transients in cortex-striatum-substantia nigra organotypic cultures.
- Utilized spontaneous up-states and somatic current injection to elicit action potentials.
- Blocked NMDA channels with high intracellular magnesium ([Mg2+]i).
Main Results:
- The delay between up-state onset and action potential generation dictates peak dendritic [Ca2+]i.
- [Ca2+]i transients peaked when action potentials occurred near up-state onset and decayed over time.
- High [Mg2+]i abolished the dependency of [Ca2+]i on action potential timing and blocked NMDA-mediated [Ca2+]i transients.
Conclusions:
- Precisely timed action potentials during striatal up-states regulate peak dendritic calcium levels.
- NMDA receptor activity is essential for this timing-dependent calcium regulation.
- This mechanism may be vital for synaptic plasticity in the corticostriatal pathway.