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.
Bibliographical noteFunding Information:
We thank W. Argraves (Medical University of South Carolina) for mouse aorta samples; J. Horton (University of California at San Francisco) for macaque monkey brain tissue; C. Beeson and Y. Peterson for modeling the structural overlap of various Alexa dyes; P. Bell for dissecting mouse kidneys; D. Leopold and A. Silva for discussion on MRI applications; R. Gourdie for discussion of Alexa Fluor 633 binding sites on artery walls; E. Vought for creating illustrations; P. Mulholland for help with using Imaris software; M. Levy and A. Schramm for comments on the manuscript. This work was supported by grants from the US National Eye Institute (R01EY017925 and R21EY020985) and funds from the Medical University of South Carolina to P.K.