Noradrenaline unmasks novel self-reinforcing motor circuits within the mammalian spinal cord

J Neurosci. 2006 May 31;26(22):5920-8. doi: 10.1523/JNEUROSCI.4623-05.2006.

Abstract

Spiking activity in motor axons represents the final central coding for muscle contraction. Recurrent collaterals in spinal cord from these same axons are known to offer a negative feedback control of motor output via a class of interposed inhibitory interneurons. Here we demonstrate that, during noradrenergic drive, a previously unknown recurrent excitatory pathway is unmasked and expressed. These excitatory projections are shown to have broad bilateral actions within and between hindlimb spinal segments and can alter ongoing pattern-generating motor behaviors. Thus, motor output strength is controlled via central positive and negative feedback loops, undoubtedly to provide a greater flexibility and dynamic range of control. That this novel function is regulated by a descending neuromodulatory transmitter indicates a conditional recruitment during certain behavioral states as part of the central noradrenergic arousal apparatus.

Publication types

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

MeSH terms

  • Aging
  • Animals
  • Animals, Newborn
  • Axons / physiology
  • Electric Stimulation
  • Motor Activity / drug effects
  • Motor Activity / physiology
  • Motor Neurons / drug effects
  • Motor Neurons / physiology*
  • Muscle Contraction / drug effects
  • Muscle Contraction / physiology
  • Norepinephrine / pharmacology*
  • Patch-Clamp Techniques
  • Rats
  • Rats, Sprague-Dawley
  • Reinforcement, Psychology
  • Spinal Cord / drug effects
  • Spinal Cord / growth & development
  • Spinal Cord / physiology*
  • Synaptic Transmission / drug effects
  • Synaptic Transmission / physiology

Substances

  • Norepinephrine