Cortically induced postsynaptic potentials in hypoglossal motoneurons after axotomy

Area of Science:

• Neuroscience
• Motor Control
• Cellular Electrophysiology

Background:

• The hypoglossal motoneurons control tongue movements, essential for functions like lapping.
• Cortical input significantly influences motoneuron activity.
• Understanding postsynaptic potential changes after nerve injury is crucial for recovery insights.

Purpose of the Study:

• To investigate the effects of cortical stimulation on postsynaptic potentials in normal and axotomized cat hypoglossal motoneurons.
• To characterize changes in excitatory and inhibitory postsynaptic potentials following hypoglossal nerve axotomy.

Main Methods:

• Electrophysiological recordings were performed on hypoglossal motoneurons in normal and axotomized cats.
• Cortical stimulation of the orbital gyrus was used to evoke postsynaptic potentials.
• Changes in excitatory postsynaptic potential (EPSP) components and inhibitory postsynaptic potential (IPSP) amplitude were analyzed at different time points post-axotomy.

Main Results:

• In normal motoneurons, cortical stimulation induced short-latency EPSPs and predominantly inhibitory postsynaptic potentials (IPSPs).
• Following axotomy, the proportion of motoneurons exhibiting both short- and long-latency EPSPs increased over time (30-80 days).
• The amplitude of cortically induced IPSPs was significantly reduced in axotomized motoneurons compared to normal ones.

Conclusions:

• Hypoglossal motoneurons exhibit altered cortical responsiveness after axotomy, with a notable increase in excitatory components.
• Reduced inhibitory postsynaptic potential amplitude suggests impaired inhibitory modulation following nerve injury.
• These findings highlight adaptive changes in neuronal excitability and synaptic integration after peripheral nerve damage.