Active properties of motoneurone dendrites: diffuse descending neuromodulation, focused local inhibition
- 29 February 2008
- journal article
- review article
- Published by Wiley in The Journal of Physiology
- Vol. 586 (5), 1225-1231
- https://doi.org/10.1113/jphysiol.2007.145078
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.Keywords
This publication has 56 references indexed in Scilit:
- Estimates of the Location of L-type Ca2+ Channels in Motoneurons of Different Sizes: A Computational StudyJournal of Neurophysiology, 2007
- Early electrophysiological abnormalities in lumbar motoneurons in a transgenic mouse model of amyotrophic lateral sclerosisEuropean Journal of Neuroscience, 2007
- The afterhyperpolarization conductance exerts the same control over the gain and variability of motoneurone firing in anaesthetized catsThe Journal of Physiology, 2006
- Localization of L-type calcium channel CaV1.3 in cat lumbar spinal cord – with emphasis on motoneuronsNeuroscience Letters, 2006
- Endogenous Monoamine Receptor Activation Is Essential for Enabling Persistent Sodium Currents and Repetitive Firing in Rat Spinal MotoneuronsJournal of Neurophysiology, 2006
- Frequency–current relationships of rat hindlimb α‐motoneuronesThe Journal of Physiology, 2006
- Simulation of Ca2+ persistent inward currents in spinal motoneurones: mode of activation and integration of synaptic inputsThe Journal of Physiology, 2006
- Effect of Nonlinear Summation of Synaptic Currents on the Input–Output Properties of Spinal MotoneuronsJournal of Neurophysiology, 2005
- Integration of synaptic and intrinsic dendritic currents in cat spinal motoneuronsBrain Research Reviews, 2002
- Motoneurons: A preferred firing range across vertebrate species?Muscle & Nerve, 2002