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Distinct short-term plasticity at two excitatory synapses in the hippocampus
P A Salin1, M Scanziani, R C Malenka
1Department of Cellular and Molecular Pharmacology, University of California, San Francisco 94143, USA.
Summary
Mossy fiber synapses in the hippocampus integrate neural activity over a wide frequency range, unlike other synapses. Long-term potentiation significantly reduces this integration capacity.
Area of Science:
- Neuroscience
- Synaptic Plasticity
- Hippocampal Circuitry
Background:
- Mossy fiber synapses in the hippocampus are crucial for information processing.
- Their role in integrating low-frequency granule cell activity remains unclear.
- Comparison with associational/commissural synapses is needed to understand functional differences.
Purpose of the Study:
- To investigate the frequency dependence of mossy fiber transmission.
- To compare frequency facilitation at mossy fiber and associational/commissural synapses.
- To determine the role of Ca2+ and CaMKII in mossy fiber frequency facilitation.
Main Methods:
- Electrophysiological recordings in the CA3 region of the hippocampus.
- Paired-pulse and frequency facilitation protocols were used.
- Investigated the role of intracellular calcium and Ca2+/calmodulin-dependent kinase II.
Main Results:
- Mossy fiber synapses exhibit greater paired-pulse facilitation than associational/commissural synapses.
- Mossy fiber synapses show significant frequency facilitation at lower frequencies (once every 40s) compared to associational/commissural synapses (once every 10s).
- Frequency facilitation depends on intraterminal Ca2+ rise and CaMKII activation, and is reduced by long-term potentiation.
Conclusions:
- The mossy fiber synapse effectively integrates neural activity across a broad frequency spectrum.
- Long-term potentiation diminishes the dynamic range of mossy fiber synaptic integration.
- These findings highlight the plasticity and dynamic nature of hippocampal synaptic transmission.