This Article Full Text (PDF) All Versions of this Article: 1073858408314986v1 14/3/264    most recent References Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via HighWire Google Scholar Articles by Heckman, C.J. Articles by Schuster, J. PubMed PubMed Citation Articles by Heckman, C.J. Articles by Schuster, J. Social Bookmarking                   What's this?

Persistent Inward Currents in Spinal Motoneurons and Their Influence on Human Motoneuron Firing Patterns

Department of Physiology, Northwestern University Feinberg School of Medicine, c-heckman{at}northwestern.edu, Department of Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, Illinois

Michael Johnson

Department of Physiology, Northwestern University Feinberg School of Medicine, c-heckman{at}northwestern.edu, Department of Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, Illinois

Carol Mottram

Department of Physiology, Northwestern University Feinberg School of Medicine, c-heckman{at}northwestern.edu, Department of Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, Illinois

Jenna Schuster

Department of Physiology, Northwestern University Feinberg School of Medicine, c-heckman{at}northwestern.edu, Department of Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, Illinois

Persistent inward currents (PICs) are present in many types of neurons and likely have diverse functions. In spinal motoneurons, PICs are especially strong, primarily located in dendritic regions, and subject to particularly strong neuromodulation by the monoamines serotonin and norepinephrine. Because motoneurons drive muscle fibers, it has been possible to study the functional role of their PICs in motor output and to identify PIC-mediated effects on motoneuron firing patterns in human subjects. The PIC markedly amplifies synaptic input, up to fivefold or more, depending on the level of monoaminergic input. PICs also tend to greatly prolong input time course, allowing brief inputs to initiate long-lasting self-sustained firing (i.e., bistable behavior). PIC deactivation usually requires inhibitory input and PIC amplitude can increase to repeated activation. All of these behaviors markedly increase motoneuron excitability. Thus, in the absence of monoaminergic input, motoneuron excitability is very low. Yet PICs have another effect: once active, they tend to sharply limit efficacy of additional synaptic input. All of these PIC effects have been detected in motoneuron firing patterns in human subjects and, hence, PICs are likely a fundamental component of normal motor output. NEUROSCIENTIST 14(3):264–275, 2008. DOI: 10.1177/1073858408314986

Key Words: Neuromodulation • Spinal neuron • Motor unit • Serotonin • Norepinephrine • Electrophysiology

CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				J. W. Worrell and R. B. Levine Characterization of Voltage-Dependent Ca2+ Currents in Identified Drosophila Motoneurons In Situ J Neurophysiol, August 1, 2008; 100(2): 868 - 878. [Abstract] [Full Text] [PDF]