Alterations of blood flow and intracranial pressure during brain edema

Brain edema (BE) induces disturbances in cerebral capillary blood flow (Bullock et al, Journal of neurology, neurosurgery, and psychiatry, 1991). The purpose of this study is to test the hypotheses that astrocytes modulate blood flow dynamics in BE. Several strains of genetically modified mice will be used to unravel the molecular mechanism by which astrocytes regulate vascular dynamics in BE. The blood flow will be measured using two-photon laser microscopy using bolus injections of texas red (Gutierrez-Jimenez et al, Journal of Cerebral Blood Flow and Metabolism, 2016: article attached) and laser doppler. In the same experiment, we will investigate the calcium (Ca2+) transients in the astrocytes using genetically encoded calcium indicators (GECI) to see if Ca2+ transients correlate with blood flow changes and edema development. The possible involvement of aquaporin-4 (AQP4), its anchors alpha-syntrophin and dystrophin, and IP3R2 will be assessed by using gene knockout animals. Similar experiments have already been performed in FOTS 7814, whereby BE is induced through i.p. injections of distilled water. In the current project we will use a reduced osmotic challenge compared to that in FOTS 7814 so that BE develops more slowly and becomes less severe.. Specifically, we will inject 10 % of bodyweight with 25% saline solution in sterile water i.p.. Using this protocol the alterations in blood flow and Ca2+ transients in astrocytes will be imaged by two-photon microscopy, both in control and mutant mice. Since cerebral blood flow is tightly coupled to intracranial pressure (ICP) we will also assess ICP in this model of BE. The protocol of ICP is similar to that of FOTS 11180.