Bursting Dynamics Based on the Persistent Na⁺ and Na⁺/K⁺ Pump Currents: A Dynamic Clamp Approach

Area of Science:

• Neuroscience
• Computational Biology
• Electrophysiology

Background:

• Rhythmic motor functions, like heartbeat and breathing, are generated by central pattern generators (CPGs).
• Sustained neuronal bursting requires precise regulation of intracellular sodium (Na+) levels.
• The persistent sodium current (I_NaP) and the Na⁺/K⁺ pump current (I_pump) are key players in regulating Na+ homeostasis during bursting.

Purpose of the Study:

• To investigate the hypothesis that the interaction between I_NaP and I_pump supports functional bursting in CPGs.
• To elucidate the roles of I_NaP and I_pump in the leech heartbeat CPG interneurons (HN neurons).

Main Methods:

• Utilized a combination of electrophysiology, computational modeling, and dynamic clamp techniques.
• Applied dynamic clamp to living, synaptically isolated HN neurons to manipulate I_pump and I_NaP in real time.

Main Results:

• A joint increase in I_NaP and I_pump induced a transition to a new bursting regime with higher spike frequency and larger membrane potential oscillations.
• Elevated I_pump accelerated the rhythm by reducing burst duration (BD) and interburst interval (IBI).

Conclusions:

• The interplay between I_NaP and I_pump is crucial for generating and modulating rhythmic bursting in CPGs.
• These currents provide a flexible mechanism for adjusting CPG output in response to changing physiological demands.