Quantification of early blood-brain barrier disruption by in situ brain perfusion technique

Osmotic disruption is currently being used to circumvent the blood-brain barrier (BBB) and enhance the delivery of therapeutic molecules in human brains. To date, however, the time course during the early phase of disruption has not been clarified. In order to demonstrate the rapid change in cerebrovascular permeability after BBB disruption in rats, we developed a method of in situ brain perfusion to demonstrate the earliest reversibility in cerebrovascular permeability. Osmotic BBB disruption was attained by intracarotid infusion of hypertonic mannitol. Perfusate containing [14C]-sucrose was infused at different time points following osmotic stress followed by measuring cerebrovascular permeability. The earliest BBB disruption was seen to occur 5 min after osmotic stress, after which the exact time course of cerebrovascular reversibility was studied. The protocol reported here, in contrast with those reported in previous studies, was shown to be qualitative, simple, and fast. In addition, the method can be applied to measure any low BBB permeability molecules. This protocol should be helpful for any research focused on enhancing drug delivery into the brain following osmotic BBB disruption.