Intrinsic excitability differs between murine hypoglossal and spinal motoneurons

Area of Science:

• Neuroscience
• Motor Control
• Electrophysiology

Background:

• Motoneurons control diverse behaviors and exhibit varying disease/aging vulnerability.
• Hypoglossal motoneurons (HMs) and spinal motoneurons (SMs) serve distinct motor functions but lack direct electrophysiological comparison.
• Existing research predominantly focuses on HMs over SMs, particularly in adult animals.

Purpose of the Study:

• To directly compare the electrophysiological properties of HMs and SMs in neonatal mice.
• To elucidate functional differences in motoneuron pools based on their distinct roles.

Main Methods:

• Whole-cell patch-clamp recordings were performed on age-matched neonatal mice (P7-P10).
• Passive membrane properties, afterhyperpolarization, action potential (AP) characteristics, and firing frequencies were analyzed.

Main Results:

• Passive membrane properties and afterhyperpolarization were similar between HMs and SMs.
• HMs displayed narrower APs and faster AP upstrokes compared to SMs.
• HMs achieved higher AP firing frequencies under both step and ramp current injections.

Conclusions:

• Despite similar passive properties, HMs and SMs exhibit significant differences in active electrophysiological properties.
• These differences suggest distinct ion channel compositions tailored to the specific mechanical demands of their respective muscle targets.
• Functional specialization of motoneuron pools is supported by unique electrophysiological profiles.