Neurovascular coupling and CO₂ interrogate distinct vascular regulations

Area of Science:

• Neuroscience
• Physiology
• Biochemistry

Background:

• Neurovascular coupling (NVC) maps brain activity but its mechanisms are debated.
• A hypothesis suggests metabolically produced carbon dioxide (CO2) contributes to NVC.

Purpose of the Study:

• To investigate the role of CO2 in mediating NVC.
• To examine the temporal relationship between CO2-induced changes and NVC.

Main Methods:

• Combined functional ultrasound and two-photon imaging in mouse barrel cortex.
• Measured vessel diameter, blood flow, pH, and calcium signals during CO2 challenge and whisker stimulation.

Main Results:

• Brief hypercapnia caused reversible acidification of arteriole walls and surrounding space preceding dilation.
• This acidification did not affect NVC triggered by whisker stimulation.
• NVC persisted even with continuous CO2 inflow.

Conclusions:

• CO2 is not involved in the mechanism of NVC.
• The observed acidification lag suggests CO2 is not the primary driver of NVC.