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Active properties of motoneurone dendrites: diffuse descending neuromodulation, focused local inhibition. J Physiol 2008 Mar 01;586(5):1225-31

Date

10/20/2007

Pubmed ID

17947305

Pubmed Central ID

PMC2375668

DOI

10.1113/jphysiol.2007.145078

Scopus ID

2-s2.0-40049108138 (requires institutional sign-in at Scopus site)   104 Citations

Abstract

The dendrites of spinal motoneurones are highly active, generating a strong persistent inward current (PIC) that has an enormous impact on processing of synaptic input. The PIC is subject to regulation by descending neuromodulatory systems releasing the monoamines serotonin and noradrenaline. At high monoaminergic drive levels, the PIC dominates synaptic integration, generating an intrinsic dendritic current that is as much as 5-fold larger than the current entering via synapses. Without the PIC, motoneurone excitability is very low. Presumably, this descending control of the synaptic integration via the PIC is used to adjust the excitability (gain) of motoneurones for different motor tasks. A problem with this gain control is that monoaminergic input to the cord is very diffuse, affecting many motor pools simultaneously, probably including both agonists and antagonists. The PIC is, however, exquisitely sensitive to the reciprocal inhibition mediated by length sensitive muscle spindle Ia afferents and Ia interneurones. Reciprocal inhibition is tightly focused, shared only between strict mechanical antagonists, and thus can act to 'sculpt' specific movement patterns out of a background of diffuse neuromodulation. Thus it is likely that motoneurone gain is set by the interaction between diffuse descending neuromodulation and specific and focused local synaptic inhibitory circuits.

Author List

Heckman CJ, Hyngstrom AS, Johnson MD

Author

Allison Hyngstrom PhD Associate Professor in the Physical Therapy department at Marquette University




MESH terms used to index this publication - Major topics in bold

Animals
Cats
Dendrites
Humans
Interneurons
Motor Neurons
Neurotransmitter Agents
Synaptic Transmission