Spinal Cord Injury Significantly Alters the Properties of Reticulospinal Neurons: I. Biophysical Properties, Firing...

Area of Science:

• Neuroscience
• Regenerative Medicine
• Comparative Biology

Background:

• Spinal cord injury (SCI) impairs neuronal function and locomotor recovery.
• Reticulospinal (RS) neurons are crucial for locomotion and axonal regeneration after SCI in larval lampreys.

Purpose of the Study:

• To compare the electrophysiological properties of uninjured and injured RS neurons following SCI in larval lampreys.
• To understand how SCI-induced changes in RS neuron biophysics influence neuronal function and potentially support regeneration.

Main Methods:

• Electrophysiological recordings from identified RS neuron pairs (uninjured vs. injured) after spinal cord hemi-transection (HT).
• Analysis of neuronal firing patterns, membrane properties (V_REST, time constant, capacitance), action potential characteristics, and synaptic responses.
• Investigated the role of slow afterhyperpolarization (sAHP) in altered neuronal properties.

Main Results:

• Injured RS neurons exhibited altered firing patterns, hyperpolarized resting potential, longer membrane time constants, increased action potential thresholds, and reduced firing frequencies.
• A distinct "injury phenotype" was observed in RS neurons, characterized by reduced excitability.
• Synaptic responses to trigeminal stimulation remained largely unchanged between injured and uninjured RS neurons.

Conclusions:

• SCI induces significant biophysical changes in lamprey RS neurons, creating an "injury phenotype" that reduces excitability.
• These alterations are hypothesized to reduce calcium influx and promote conditions favorable for axonal regeneration and functional recovery.