1. Sodium-Mediated Plateau Potentials in Lumbar Motoneurons of Neonatal Rats
- Author
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Aziz Moqrich, Frédéric Brocard, Sabrina Tazerart, Mouloud Bouhadfane, and Laurent Vinay
- Subjects
Boron Compounds ,Hot Temperature ,Calcium Channels, L-Type ,TRPV2 ,Action Potentials ,TRPV Cation Channels ,TRPV ,Afterdepolarization ,Transient receptor potential channel ,Plateau potentials ,Animals ,Channel blocker ,Rats, Wistar ,Motor Neurons ,Voltage-dependent calcium channel ,Probenecid ,Chemistry ,General Neuroscience ,Sodium ,Depolarization ,Articles ,Calcium Channel Blockers ,Flufenamic Acid ,Rats ,Spinal Cord ,Anesthesia ,Biophysics ,Calcium - Abstract
The development and the ionic nature of bistable behavior in lumbar motoneurons were investigated in rats. One week after birth, almost all (∼80%) ankle extensor motoneurons recorded in whole-cell configuration displayed self-sustained spiking in response to a brief depolarization that emerged when the temperature was raised >30°C. The effect of L-type Ca2+channel blockers on self-sustained spiking was variable, whereas blockade of the persistent sodium current (INaP) abolished them. When hyperpolarized, bistable motoneurons displayed a characteristic slow afterdepolarization (sADP). The sADPs generated by repeated depolarizing pulses summed to promote a plateau potential. The sADP was tightly associated with the emergence of Ca2+spikes. Substitution of extracellular Na+or chelation of intracellular Ca2+abolished both sADP and the plateau potential without affecting Ca2+spikes. These data suggest a key role of a Ca2+-activated nonselective cation conductance (ICaN) in generating the plateau potential. In line with this, the blockade of ICaNby flufenamate abolished both sADP and plateau potentials. Furthermore, 2-aminoethoxydiphenyl borate (2-APB), a common activator of thermo-sensitive vanilloid transient receptor potential (TRPV) cation channels, promoted the sADP. Among TRPV channels, only the selective activation of TRPV2 channels by probenecid promoted the sADP to generate a plateau potential. To conclude, bistable behaviors are, to a large extent, determined by the interplay between three currents: L-type ICa, INaP, and a Na+-mediated ICaNflowing through putative TRPV2 channels.
- Published
- 2013
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