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Precise, 3-D optogenetic control of the diameter of single arterioles

Modulation of brain arteriole diameter is critical for maintenance of cerebral blood pressure and control of hyperemia during regional neural activity. However, studies of hemodynamic function in health and disease have lacked a method to control and monitor blood flow with high spatiotemporal resolution. Here, we describe a new all-optical approach to precisely control and monitor arteriolar contractility in vivo using combined two-photon optogenetics and imaging. The expression of the excitatory opsin, ReaChR, in vascular smooth muscle cells enabled rapid and repeated vasoconstriction following brief light pulses. Targeted two-photon activation of ReaCHR using a spatial light modulator (SLM) produced highly localized constrictions when targeted to individual arteries within the neocortex. We demonstrate the utility of this method for examining arteriole contractile dynamics and creating transient blood flow reductions. Additionally, we show that optogenetic constriction can offset or completely block sensory stimulus evoked vasodilation, providing a valuable tool to dissociate blood flow changes from neural activity.