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

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...

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Published in:Journal of neurophysiology 2012-10, Vol.108 (8), p.2191-2202
Main Authors: Abbinanti, Matthew D, Zhong, Guisheng, Harris-Warrick, Ronald M
Format: Article
Language:English
Subjects:
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
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Summary: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.
ISSN:0022-3077
1522-1598
1522-1598
DOI:10.1152/jn.00336.2012