Alterations in synaptic input to motoneurons during partial spinal cord injury

Area of Science:

• Neuroscience
• Spinal Cord Injury Research
• Motor Control

Background:

• Spasticity following spinal cord injury (SCI) and stroke significantly impacts motor function.
• Existing animal models do not fully replicate the complex spasticity observed in human SCI and stroke patients.
• Understanding the cellular mechanisms underlying motor deficits is crucial for developing effective treatments.

Purpose of the Study:

• To develop and validate an acute animal model of spinal cord injury that mimics human spasticity.
• To investigate the cellular mechanisms responsible for disrupted motoneuron recruitment and rate modulation in this model.
• To explore potential therapeutic strategies for mitigating motor deficits.

Main Methods:

• Development of an acute dorsal hemisection spinal cord injury model in decerebrate cats.
• Combined experimental and computational simulation approach to study motoneuron function.
• Analysis of synaptic input organization and intrinsic motoneuron properties.

Main Results:

• The animal model accurately replicates spasticity seen in human SCI and stroke.
• Severe disruptions in motoneuron recruitment and rate modulation patterns were observed.
• Cellular studies indicated that altered synaptic input, not intrinsic motoneuron properties, underlies these deficits.
• Computer simulations demonstrated that altered inhibitory synaptic input can cause significant motor control disruptions.

Conclusions:

• The developed animal model is a valuable tool for studying SCI-induced spasticity.
• Dysfunctional synaptic input to motoneurons is the primary cause of motor deficits.
• Monoaminergic systems, involving noradrenaline and serotonin, are critical for maintaining spinal circuit inhibition.
• Pharmacological targeting of monoamines holds promise for treating spasticity and improving motor function after SCI.