Sodium-mediated plateau potentials in lumbar motoneurons of neonatal rats.

نویسندگان

  • Mouloud Bouhadfane
  • Sabrina Tazerart
  • Aziz Moqrich
  • Laurent Vinay
  • Frédéric Brocard
چکیده

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 Ca(2+) channel blockers on self-sustained spiking was variable, whereas blockade of the persistent sodium current (I(NaP)) 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 Ca(2+) spikes. Substitution of extracellular Na(+) or chelation of intracellular Ca(2+) abolished both sADP and the plateau potential without affecting Ca(2+) spikes. These data suggest a key role of a Ca(2+)-activated nonselective cation conductance ((CaN)) in generating the plateau potential. In line with this, the blockade of (CaN) by 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 I(Ca), I(NaP), and a Na(+)-mediated I(CaN) flowing through putative TRPV2 channels.

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عنوان ژورنال:
  • The Journal of neuroscience : the official journal of the Society for Neuroscience

دوره 33 39  شماره 

صفحات  -

تاریخ انتشار 2013