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Presynaptic morphological changes associated with long-term synaptic facilitation are triggered by actin
1Department of Pharmacology and Center for Neurobiology and Behavior, Columbia University and New York State Psychiatric Institute, New York, New York 10032, USA.
Summary
Serotonin triggers long-term memory formation by inducing persistent changes in presynaptic varicosities, essential for new synaptic growth. Actin polymerization is critical for these morphological changes in mechanosensory neurons.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- Long-term synaptic plasticity, crucial for learning and memory, involves morphological changes in neurons.
- The precise mechanisms initiating and sustaining these structural alterations remain largely unknown.
Purpose of the Study:
- To investigate the mechanisms underlying the formation of new synaptic varicosities during long-term synaptic facilitation.
- To determine the role of actin polymerization in serotonin-induced morphological changes in mechanosensory neuron axons.
Main Methods:
- Repeated imaging of axonal arbors in Aplysia mechanosensory neurons.
- Application of serotonin to induce long-term synaptic facilitation.
- Treatment with cytochalasin D to inhibit actin polymerization.
Main Results:
- New synaptic varicosities formed exclusively from existing varicosities through splitting or outgrowth.
- Cytochalasin D treatment prevented these morphological changes.
- Morphological changes and facilitation were restored after cytochalasin D removal, indicating persistent serotonin effects.
Conclusions:
- Serotonin induces persistent presynaptic effects that promote actin polymerization.
- Actin polymerization is essential for the morphological adaptations underlying long-term synaptic facilitation.
- These findings elucidate key molecular mechanisms in the cellular basis of learning and memory.