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Related Experiment Videos

Persistent inward currents in motoneuron dendrites: implications for motor output.

C J Heckmann1, Monica A Gorassini, David J Bennett

  • 1Department of Physiology, Neuroscience Institute, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA. c-heckman@northwestern.edu

Muscle & Nerve
|March 1, 2005
PubMed
Summary

Motoneuron dendrites generate strong persistent inward currents (PICs) modulated by brainstem monoamines, influencing motor unit firing. These PICs recover after spinal cord injury, potentially relating to spasticity.

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Area of Science:

  • Neuroscience
  • Motor Control
  • Cellular Physiology

Background:

  • Motoneuron dendrites were previously considered passive.
  • Dendrites possess voltage-dependent channels capable of generating persistent inward currents (PICs).

Purpose of the Study:

  • To investigate the role of dendritic PICs in motoneuron excitability and motor unit firing patterns.
  • To explore the modulation of dendritic PICs by brainstem neuromodulatory input.
  • To examine the recovery of PICs after spinal cord injury and their potential link to spasticity.

Main Methods:

  • Analysis of voltage-dependent channels in motoneuron dendrites.
  • Investigation of neuromodulatory effects (serotonin, norepinephrine) on PIC amplitude.
  • Study of motor unit firing patterns in relation to PIC activation and deactivation.

Related Experiment Videos

  • Assessment of PIC recovery following spinal cord injury.

    • Main Results:

    • Dendritic PICs significantly influence motor unit recruitment and derecruitment, creating linear firing rate increases above threshold.
    • PIC amplitude is proportional to brainstem monoaminergic input.
    • Dendritic PICs enable sustained tonic firing with minimal synaptic input, especially in low-threshold units.
    • Synaptic inhibition can readily deactivate dendritic PICs.
    • PICs recover near-normal amplitudes months after spinal cord injury, despite loss of brainstem control.

    Conclusions:

    • Dendritic PICs are crucial active contributors to motoneuron function, not passive conduits.
    • Brainstem neuromodulation via monoamines dynamically controls motoneuron excitability through dendritic PICs.
    • The recovery of dendritic PICs post-spinal cord injury may contribute to the development of spasticity.