Potassium buffering in the neurovascular unit: models and sensitivity analysis.

Area of Science:

• Neuroscience
• Computational Biology
• Physiology

Background:

• Astrocytes are key in neural and neurovascular communication.
• Potassium transport is a fundamental astrocyte function.
• Specific potassium channels (Na-K, NKCC, Kir, BK) are located in different astrocyte regions.

Purpose of the Study:

• To develop a detailed computational model of potassium flow within the neurovascular unit.
• To investigate the roles of different potassium transporters and channels in astrocyte function.
• To explain experimental observations like functional hyperemia and synaptic K+ undershoot.

Main Methods:

• Computational modeling of potassium dynamics in the synaptic region, astrocytes, and arterioles.
• Simulation of neural activity and blockade of specific channels.
• High-dimensional stochastic sensitivity analysis to assess parametric uncertainty.

Main Results:

• The model successfully reproduces functional hyperemia, synaptic K+ undershoot, and neurally induced astrocyte hyperpolarization during Kir blockade.
• Astrocytic Kir channels are crucial for the rapid onset of functional hyperemia, while BK channels maintain dilation.
• Excessive astrocytic uptake via Na-K and NKCC pumps, balanced by Kir, explains K+ undershoot.

Conclusions:

• Astrocytic potassium transport mechanisms are central to neurovascular coupling.
• The model provides insights into the distinct roles of Kir and BK channels in regulating blood flow.
• The study highlights the complex interplay of ion transport in maintaining brain homeostasis and identifies potential model limitations.