title: Postnatal emergence of serotonin-induced plateau potentials in commissural interneurons of the mouse spinal cord.
abstract: 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.
authors: Dept. of Neurobiology and Behavior, Cornell Univ., Ithaca, NY 14853, USA.
authors: Matthew D
authors: MD
authors: Abbinanti
authors: Guisheng
authors: G
authors: Zhong
authors: Ronald M
authors: RM
authors: Harris-Warrick
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D007395:Interneurons / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009543:Nifedipine / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D012701:Serotonin / Q000494:pharmacology*; D013116:Spinal Cord / Q000166:cytology / Q000254:growth & development / Q000502:physiology*
chemical_list: D002121:Calcium Channel Blockers; D012701:Serotonin; D009543:Nifedipine; D011188:Potassium; D002118:Calcium