An artery-specific fluorescent dye for studying neurovascular coupling

The authors report Alexa Fluor 633 hydrazide to be artery-specific and use it to measure arteriole dilation dynamics in vivo in response to visual stimuli in mouse, rat and cat neocortex. They find that sensory stimulus–evoked arteriole dilation reduces the fluorescence recorded from underlying neurons. We demonstrate that Alexa Fluor 633 hydrazide (Alexa Fluor 633) selectively labels neocortical arteries and arterioles by binding to elastin fibers. We measured sensory stimulus–evoked arteriole dilation dynamics in mouse, rat and cat visual cortex using Alexa Fluor 633 together with neuronal activity using calcium indicators or blood flow using fluorescein dextran. Arteriole dilation decreased fluorescence recorded from immediately underlying neurons, representing a potential artifact during neuronal functional imaging experiments.