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Structural changes at dendritic spine synapses during long-term potentiation
Kristen M Harris1, John C Fiala, Linnaea Ostroff
1Synapses and Cell Signaling Program, Medical College of Georgia, Institute of Molecular Medicine and Genetics, 1120 15th Street, CB-2803, Augusta, GA 30912-2630, USA. kharris@mail.mcg.edu
Summary
Long-term potentiation (LTP) involves synapse enlargement, not spine splitting, with new dendritic protrusions minimally increasing connectivity. Polyribosomes identify existing synapses that enlarge to sustain synaptic strength during LTP.
Area of Science:
- Neuroscience
- Cell Biology
- Synaptic Plasticity
Background:
- Long-term potentiation (LTP) is a key cellular mechanism for memory formation.
- Understanding the structural changes underlying LTP is crucial for neuroscience research.
- Previous hypotheses focused on dendritic spine splitting as the primary structural change during LTP.
Purpose of the Study:
- To investigate the structural basis of long-term potentiation (LTP) in immature rat hippocampal slices.
- To evaluate the roles of dendritic spine changes and polyribosomes in synaptic plasticity.
- To determine the relative contributions of enhanced connectivity and synapse enlargement to LTP.
Main Methods:
- Electrophysiological recordings in immature rat hippocampal slices.
- High-resolution imaging to observe dendritic spine morphology.
- Analysis of polyribosome localization within dendritic spines.
Main Results:
- Dendritic spines do not split during LTP; instead, new protrusions form, offering a minor increase in connectivity.
- These 'same dendrite multiple synapse boutons' do not accumulate with maturation and do not fully explain LTP.
- Polyribosomes within dendritic spines are involved in identifying existing synapses that undergo significant enlargement.
- Synapse enlargement accounts for over 30% increase in synaptic strength, a more substantial effect than enhanced connectivity.
Conclusions:
- LTP involves both enhanced connectivity and significant synapse enlargement.
- Synapse enlargement is the dominant structural mechanism contributing to LTP.
- Polyribosomes play a critical role in regulating synapse-specific structural modifications during plasticity.