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Activity-dependent recruitment of silent synapses
J M Wojtowicz1, B R Smith, H L Atwood
1Department of Physiology, University of Toronto, Ontario, Canada.
Annals of the New York Academy of Sciences
|January 1, 1991
Summary
Tetanic stimulation enhances crayfish neuromuscular junctions by recruiting new synapses and increasing release probability. This long-lasting synaptic plasticity requires protein phosphorylation, not just calcium influx.
Area of Science:
- Neuroscience
- Synaptic Plasticity
- Cellular Neuroscience
Background:
- Tetanic stimulation induces long-lasting synaptic enhancement at the crayfish neuromuscular junction.
- This enhancement is presynaptic, affecting quantal content but not quantal size.
Purpose of the Study:
- To investigate the mechanisms underlying long-lasting synaptic enhancement.
- To determine the role of calcium, adenylate cyclase, and protein kinase in this process.
- To elucidate the changes in synaptic transmission during enhancement.
Main Methods:
- Tetanic stimulation (10-20 Hz) of crayfish neuromuscular junction.
- Presynaptic injection of adenylate cyclase inhibitors and protein kinase inhibitors.
- Analysis of quantal events using binomial and refined statistical methods.
- Comparison with short-term facilitation.
Main Results:
- Long-lasting enhancement is blocked by inhibiting adenylate cyclase or cyclic AMP-dependent protein kinase.
- Calcium entry alone is insufficient for enhancement.
- Both the number of responding units and release probability increase during enhancement.
- Tetanic activity recruits unresponsive synapses.
Conclusions:
- Protein phosphorylation is essential for long-lasting synaptic changes.
- Tetanic stimulation can recruit previously unresponsive synapses.
- The number of active synapses can increase beyond morphologically defined ones.