Opposed hemodynamic responses following increased excitation and parvalbumin-based inhibition

Understanding cellular contributions to hemodynamic activity is essential for interpreting blood-based brain mapping signals. Optogenetic studies examining cell-specific influences on local hemodynamics have reported that excitatory activity results in cerebral perfusion and blood volume increase, while inhibitory activity contributes to both vasodilation and vasoconstriction. How specific subpopulations of interneurons regulate the brain's blood supply is less examined. Parvalbumin interneurons are the largest subpopulation of GABAergic neurons in the brain, critical for brain development, plasticity, and long-distance excitatory neurotransmission. Despite their essential role in brain function, the contribution of parvalbumin neurons to neurovascular coupling has been relatively unexamined. Using optical intrinsic signal imaging and laser speckle contrast imaging, we photostimulated awake and anesthetized transgenic mice expressing channelrhodopsin under a parvalbumin promoter. Increased parvalbumin activity reduced local oxygenation, cerebral blood volume, and cerebral blood flow. These negative hemodynamic responses were consistent within and across mice and reproducible across a broad range of photostimulus parameters. However, the sign and magnitude of the hemodynamic response resulting from increased parvalbumin activity depended on the type and level of anesthesia used. Opposed hemodynamic responses following increased excitation or parvalbumin-based inhibition suggest unique contributions from different cell populations to neurovascular coupling.

Automated summary

Understanding cellular contributions to hemodynamic activity is crucial for interpreting blood-based brain mapping signals. Studies have shown that excitatory activity increases cerebral perfusion and blood volume, while inhibitory activity contributes to vasodilation and vasoconstriction. Parvalbumin interneurons, as the largest subpopulation of GABAergic neurons in the brain, play a critical role in brain function. Research has found that increased activity in parvalbumin neurons leads to a reduction in local oxygenation, cerebral blood volume, and cerebral blood flow.