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Toxin-resistant calcium currents in embryonic mouse sensory neurons
C Hilaire1, S Diochot, G Desmadryl
1Laboratoire de médecine expérimentale, Institut de Biologie, C.N.R.S.UPR 9008, I.N.S.E.R.M. U 249, Montpellier, France.
Neuroscience
|September 1, 1997
Summary
Researchers identified a novel toxin-resistant calcium current in sensory neurons. This current, distinct from T-type, shares properties with alpha(1E) subunit channels, suggesting a potential link in dorsal root ganglion neurons.
Area of Science:
- Neuroscience
- Molecular Biology
- Ion Channel Physiology
Background:
- Dorsal root ganglion (DRG) neurons express various high-voltage-activated calcium channels.
- Specific calcium channel subtypes mediate distinct physiological functions in sensory neurons.
- Understanding calcium channel composition is crucial for deciphering neuronal excitability and signaling.
Purpose of the Study:
- To characterize toxin-insensitive calcium currents in embryonic dorsal root ganglion neurons.
- To identify residual calcium currents after blockade of N-, L-, and P/Q-type channels.
- To investigate the properties and potential molecular identity of a toxin-resistant calcium current.
Main Methods:
- Acutely dissociated embryonic dorsal root ganglion neurons were used.
- Pharmacological blockade of N-, L-, and P/Q-type calcium currents using specific toxins (omega-conotoxin-GVIA, nitrendipine, omega-agatoxin-IVA, omega-conotoxin-MVIIC).
- Electrophysiological characterization of residual calcium currents, including activation, inactivation, ion selectivity, and sensitivity to blockers (cadmium, nickel, amiloride).
Main Results:
- Two residual calcium currents, T-type and a toxin-resistant current, were observed after toxin application.
- The toxin-resistant current exhibited inactivating and sustained components.
- This current showed intermediate activation/inactivation kinetics, similar ion permeability to T-type, high sensitivity to cadmium/nickel, and amiloride insensitivity.
- Properties align with calcium channels containing alpha(1E) subunits, which were detected in these neurons.
Conclusions:
- Embryonic dorsal root ganglion neurons express a toxin-resistant calcium current alongside T-type currents.
- This toxin-resistant current displays characteristics consistent with calcium channels containing alpha(1E) subunits.
- A component of the toxin-resistant calcium channels in sensory neurons may be closely related to alpha(1E) subunit-containing channels.