increased permeability of blood vessels after reversible electroporation is facilitated by alterations in endothelial celltocell junctions delivery of electric field pulses ie electroporation ep to tissues has been shown to have a blood flow modifying effect indeed the diameter of blood vessels exposed to ep is immediately reduced resulting in blood flow abrogation followed by an increase in vascular permeability the main cause of the increased permeability remains unknown the aim of this study was to determine whether the in vivo effects of ep on permeability of blood vessels are linked to the permeabilization of endothelial cells membrane ec andor disruption of celltocell junctions we used a dorsal window chamber model in c57bl6 mice coupled with multiphoton microscopy and fluorescently labelled antibodies against pecam1 cd31 to visualize endothelial celltocell junctions clinically validated ep parameters were used and behavior of celltocell junctions in combination with leakage of 70kda fluorescein isothiocyanate labelled dextran fd was followed in time after ep a constriction of blood vessels was observed and correlated with the change in the shape of ecs this was followed by an increase in permeability of blood vessels for 70kda fd and a decrease in the volume of labelled celltocell junctions both parameters returned to pretreatment values in 50 of mice for the remaining 50 we hypothesize that disruption of celltocell junctions after ep may trigger the platelet activation cascade our findings show for the first time in vivo that alterations in celltocell junctions play an important role in the response of blood vessels to ep and explain their efficient permeabilization