Postnatal emergence of serotonin-induced plateau potentials in commissural interneurons of the mouse spinal cord

J Neurophysiol. 2012 Oct;108(8):2191-202. doi: 10.1152/jn.00336.2012. Epub 2012 Jul 25.


Most studies of the mouse hindlimb locomotor network have used neonatal (P0-5) mice. In this study, we examine the postnatal development of intrinsic properties and serotonergic modulation of intersegmental commissural interneurons (CINs) from the neonatal period (P0-3) to the time the animals bear weight (P8-10) and begin to show adult walking (P14-16). CINs show an increase in excitability with age, associated with a decrease in action potential halfwidth and appearance of a fast component to the afterhyperpolarization at P14-16. Serotonin (5-HT) depolarizes and increases the excitability of most CINs at all ages. The major developmental difference is that serotonin can induce plateau potential capability in P14-16 CINs, but not at younger ages. These plateau potentials are abolished by nifedipine, suggesting that they are mediated by an L-type calcium current, I(Ca(L)). Voltage-clamp analysis demonstrates that 5-HT increases a nifedipine-sensitive voltage-activated calcium current, I(Ca(V)), in P14-16 CINs but does not increase I(Ca(V)) in P8-10 CINs. These results, together with earlier work on 5-HT effects on neonatal CINs, suggest that 5-HT increases the excitability of CINs at all ages studied, but by opposite effects on calcium currents, decreasing N- and P/Q-type calcium currents and, indirectly, calcium-activated potassium current, at P0-3 but increasing I(Ca(L)) at P14-16.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Action Potentials / drug effects
  • Action Potentials / physiology*
  • Animals
  • Calcium / metabolism
  • Calcium Channel Blockers / pharmacology
  • Interneurons / physiology*
  • Mice
  • Mice, Inbred C57BL
  • Nifedipine / pharmacology
  • Potassium / metabolism
  • Serotonin / pharmacology*
  • Spinal Cord / cytology
  • Spinal Cord / growth & development
  • Spinal Cord / physiology*


  • Calcium Channel Blockers
  • Serotonin
  • Nifedipine
  • Potassium
  • Calcium