Three-dimensional reconstruction of the rat brain cortical microcirculation in vivo

We used confocal laser scanning microscopy (CLSM) to investigate the morphology and three-dimensional relationships of the microcirculation of the superficial layers of the rat brain cortex in vivo. In anesthetized rats equipped with a closed cranial window (dura mater removed), after i.v. injection of 3 mg/100 g of body weight of fluorescein in 0.5 ml of saline, serial optical sections of the brain cortex intraparenchymal microcirculation were taken. Excitation was at a wavelength of 488 nm (argon laser), and emission was collected above 515 nm. CLSM provided images of brain vessels with sufficient signal-to-noise ratio for three-dimensional reconstructions down to a depth of 250 μm beneath the surface of the brain. Compared to conventional fluorescence microscopy, CLSM has a much higher axial resolution and higher depth of penetration. Laser light-induced intravascular aggregates, irregularities of erythrocyte flow, or microvascular occlusions (“light and dye injury”) were not apparent in the current experimental paradigm. CLSM is a promising new tool for in vivo visualization of the cerebral microcirculation. Future studies have to characterize the potential damage to the tissue caused by the cranial window preparation and light and dye mechanisms