Serotonin modulates the properties of ascending commissural interneurons in the neonatal mouse spinal cord.
The interneuron populations that constitute the central pattern generator (CPG) for locomotion in the mammalian spinal cord are not well understood. We studied the properties of a set of commissural interneurons whose axons cross and ascend in the contralateral cord (aCINs) in the neonatal mouse. During N-methyl-D-aspartate (NMDA) and 5-HT-induced fictive locomotion, a majority of lumbar (L2) aCINs examined were rhythmically active; most of them fired in phase with the ipsilateral motoneuron pool, but some fired in phase with contralateral motoneurons. 5-HT plays a critical role in enabling the locomotor CPG to function. We found that 5-HT increased the excitability of aCINs by depolarizing the membrane potential, reducing the postspike afterhyperpolarization amplitude, broadening the action potential, and decreasing the action potential threshold. Serotonin had no significant effect on the input resistance and sag amplitude of aCINs. These results support the hypothesis that aCINs play important roles in coordinating left-right movements during fictive locomotion and thus may be component neurons in the locomotor CPG in neonatal mice.
Zhong
Guisheng
G
Dept. of Neurobiology and Behavior, Cornell Univ., W 159 Seeley G. Mudd Hall, Ithaca, NY 14853, USA.
Díaz-Ríos
Manuel
M
Harris-Warrick
Ronald M
RM
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007395:Interneurons / Q000187:drug effects / Q000502:physiology*; D008124:Locomotion / Q000187:drug effects / Q000502:physiology*; D008159:Lumbar Vertebrae / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008813:Mice, Inbred ICR; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000008:administration & dosage*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*
D012701:Serotonin