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Extracellular Ca2+ changes during transmitter application in the leech central nervous system
C Lohr1, C R Rose, J W Deitmer
1Abteilung für Allgemeine Zoologie, Universität Kaiserslautern, Germany.
Neuroscience Letters
|February 16, 1996
Summary
Excitatory neurotransmitters, but not inhibitory ones, cause significant decreases in extracellular calcium concentration ([Ca2+]e) in leech ganglia. This suggests calcium dynamics are crucial for excitatory transmission in the central nervous system.
Area of Science:
- Neuroscience
- Calcium Signaling
- Extracellular Ion Dynamics
Background:
- Extracellular calcium concentration ([Ca2+]e) plays a critical role in neuronal excitability and synaptic transmission.
- Understanding how neurotransmitters modulate [Ca2+]e is essential for deciphering neural circuit function.
Purpose of the Study:
- To investigate the effects of excitatory and inhibitory neurotransmitters on extracellular calcium levels in the leech central nervous system.
- To determine the role of potassium-evoked depolarization in modulating [Ca2+]e.
Main Methods:
- Utilized Ca(2+)-selective microelectrodes to record changes in [Ca2+]e in isolated leech segmental ganglia.
- Applied various neurotransmitters (kainate, glutamate, aspartate, carbachol, GABA, serotonin) and elevated bath potassium concentration.
Main Results:
- Excitatory agonists (kainate, glutamate, aspartate, carbachol) induced significant decreases in [Ca2+]e.
- Inhibitory transmitters (GABA, serotonin) did not alter [Ca2+]e.
- Kainate-induced [Ca2+]e changes were potentiated by repetitive application and blocked by CNQX.
- Elevated potassium concentration caused a Ni(2+)-sensitive decrease in [Ca2+]e.
Conclusions:
- Excitatory neurotransmission in the leech central nervous system is associated with substantial reductions in extracellular calcium.
- These findings highlight the dynamic interplay between neuronal activity and extracellular ion concentrations.