Efficiency considerations of using mannitol as the blood-brain barrier disrupting agent in acute two-photon in vivo studies

Mette Christina Mathiesen

Student thesis: Project on Graduate Program


The blood-brain barrier (BBB) is a highly selective barrier formed by cells lining the vasculature of the brain. Transport across the BBB is extremely restricted, which poses a challenge in drug delivery to the brain. During the process of our research, we investigated the feasibility of two strategies for inducing BBB permeability for two-photon imaging studies in mice. The first approach relied on osmotic intervention with mannitol, which is being used in the clinical scenario, whilst the second approach utilized two-photon laser-irradiation. For both methods, the effect on BBB permeability was validated by monitoring the extravasation of fluorescent dyes circulating in the blood stream. We tested different routes of delivery of mannitol to the brain (i.e. the femoral vessels or the internal carotid artery; ICA) and different parameters of injection (speed, duration) thus determining that BBB permeability can be best observed with ICA injection of 0.250ml 25% wt/vol mannitol at the rate of 0.1ml/min. However, the mannitol induced brain movement, which was observed in all treated animals, thereby raising a complication when combining the method with continuous two-photon imaging. Alternatively, we present a laser-induced BBB-disruption by point-irradiation with short pulses of high laser power applied to pial and deep cortical vessels, which allowed a targeted and reversible opening of the BBB.

EducationsPharmaceutical Biology, (Bachelor/Graduate Programme) Graduate
Publication date28 Jun 2016
Number of pages72