title: Noradrenaline unmasks novel self-reinforcing motor circuits within the mammalian spinal cord.
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.
authors.affiliation: Department of Physiology, Emory University, Atlanta, Georgia 30322, USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Machacek
authors.forename: Shawn
authors.initials: S
authors.lastname: Hochman
mesh_terms: D000375:Aging; D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000502:physiology; D004558:Electric Stimulation; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D012054:Reinforcement, Psychology; D013116:Spinal Cord / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
chemical_list: D009638:Norepinephrine