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Locus coeruleus control of spinal motor output
S J Fung1, D Manzoni, J Y Chan
1Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology, College of Veterinary Medicine, Washington State University, Pullman.
Progress in Brain Research
|January 1, 1991
Summary
The locus coeruleus (LC) system enhances motor output by exciting spinal motoneurons through alpha 1-adrenoceptors. It also boosts motor function by reducing recurrent inhibition and facilitating sensory input.
Area of Science:
- Neuroscience
- Motor Control
- Electrophysiology
Background:
- The coeruleospinal system, originating from the locus coeruleus (LC), plays a role in modulating somatomotor outflow.
- Noradrenergic LC neurons are characterized by alpha 2-receptor responses.
Purpose of the Study:
- To investigate the functional properties of the coeruleospinal system in regulating somatomotor outflow at lumbar cord levels.
- To elucidate the specific receptor mechanisms involved in LC's modulation of motor activity.
Main Methods:
- Electrophysiological techniques were employed to study coeruleospinal units.
- Activation of the coeruleospinal system and iontophoretic application of norepinephrine were used.
Main Results:
- Fast-conducting coeruleospinal units showed alpha 2-receptor responses characteristic of LC neurons.
- Coeruleospinal system activation potentiated lumbar monosynaptic reflexes and depolarized motoneurons via alpha 1-receptors.
- LC stimulation inhibited Renshaw cell activity and induced positive dorsal root potentials.
Conclusions:
- The LC augments somatomotor output primarily through alpha 1-adrenoceptor-mediated excitation of ventral horn motoneurons.
- LC enhances motor output by suppressing recurrent inhibition and presynaptically facilitating afferent transmission.