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Published on: May 25, 2011
Pharmacological dissection of high-voltage-activated Ca2+ current types in acutely dissociated rat supraoptic
1Department of Anatomy and Neurobiology, University of Tennessee, Memphis 38163, USA.
Abstract:
1. We used pharmacological blockers and whole cell voltage-clamp recordings from acutely dissociated magnocellular neurons from the rat supraoptic nucleus to test for the presence of L-, N-, P-, Q-, and R-type calcium currents. 2. We found clear evidence for L-type (dihydropyridine sensitive), N-type (blocked by omega-conotoxin (GVIA), and P-type (blocked by omega-agatoxin IVA) currents. Nifedipine blocked 28 +/- 2% (mean +/- SE) of the current, omega-conotoxin GVIA blocked 26 +/- 4%, and omega-agatoxin IVA (25-30 nM) blocked 17 +/- 4%. In addition, omega-conotoxin MVIIC blocked about half (54 +/- 2%) of the current remaining after L-, N-, and P-type currents were blocked, suggesting the presence of Q-type currents. 3. About 20% of the whole cell current was unblocked by the combination of all four blockers, suggesting the presence of a fifth current type. This residual current inactivated slowly at -10 mV.
Insights
Researchers identified multiple calcium currents in rat neurons, including L-type, N-type, and P-type. A significant portion of the current remained unidentified, suggesting a fifth calcium current type in magnocellular neurons.
Area of Science:
- Neuroscience
- Electrophysiology
Background:
- Magnocellular neurons in the supraoptic nucleus play a crucial role in regulating physiological functions.
- Understanding the types of calcium currents present in these neurons is essential for comprehending their electrical activity and function.
Purpose of the Study:
- To investigate the presence and characteristics of various calcium currents (L-, N-, P-, Q-, and R-type) in rat supraoptic nucleus magnocellular neurons.
Main Methods:
- Utilized whole-cell voltage-clamp recordings from acutely dissociated rat magnocellular neurons.
- Employed a range of pharmacological blockers specific to different calcium channel types, including nifedipine, omega-conotoxin GVIA, omega-agatoxin IVA, and omega-conotoxin MVIIC.
Main Results:
- Identified significant L-type (dihydropyridine sensitive), N-type (omega-conotoxin GVIA sensitive), and P-type (omega-agatoxin IVA sensitive) calcium currents.
- Evidence suggests the presence of Q-type currents, as indicated by blockade with omega-conotoxin MVIIC.
- Approximately 20% of the whole-cell current remained after blocking L-, N-, P-, and Q-type currents, indicating a potential fifth calcium current type.
Conclusions:
- Rat supraoptic nucleus magnocellular neurons express multiple types of voltage-gated calcium currents.
- The findings suggest the existence of at least five distinct calcium current types, with a notable residual current that inactivates slowly.
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