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Published on: May 25, 2011
Ionic channels in synaptic vesicles: are they involved in transmitter release?
R Rahamimoff1, S A DeRiemer, S Ginsburg
1Department of Physiology, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
Quarterly Journal of Experimental Physiology (Cambridge, England)
|December 1, 1989
Summary
Researchers studied cationic channels in giant vesicles from Torpedo electric organs. These P channels, voltage and calcium dependent, may facilitate gap-junction-like communication during exocytosis.
Area of Science:
- Neuroscience
- Cell Biology
- Biophysics
Background:
- Synaptic vesicles are crucial for neurotransmitter release.
- Understanding ion channel function in vesicles is key to exocytosis.
- The P channel in Torpedo electric organ vesicles was previously uncharacterized.
Purpose of the Study:
- To characterize the biophysical properties of the P channel in giant vesicles.
- To investigate the gating mechanisms and conductance states of the P channel.
- To explore potential similarities with other known ion channels and their functional implications.
Main Methods:
- Isolation of synaptic vesicles from Torpedo electric organ nerve terminals.
- Fusion of vesicles to form 'giant' vesicles for patch clamp analysis.
- Voltage-clamp recordings to study channel kinetics and conductance.
- Fractal analysis to assess channel behavior patterns.
Main Results:
- The P channel is a cationic channel with a slight preference for K+ over Na+.
- Channel opening is dependent on both voltage and intracellular calcium levels.
- Fractal analysis indicated discrete open and closed states, not fractal behavior.
- Multiple conductance levels were observed for the P channel.
Conclusions:
- The P channel exhibits complex gating and conductance properties.
- Similarities exist between the P channel, hypophyseal granule channels, and gap junction channels.
- A speculative model suggests gap-junction-like communication between secretory vesicles and the extracellular space during exocytosis.
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