Intracortical microcirculatory change induced by anesthesia in rat somatosensory cortex

Abstract

The present study aimed to characterize microcirculatory responses to anesthesia in brain tissue. With multi-photon excitation fluorescence microscopy, intra-cortical capillary dimension and red blood cell (RBC) flow were successfully visualized up to a depth of ∼0.6mmfrom the cortical surface in rats anesthetized with either isoflurane or a-chloralose. We observed that the diameter of the major cerebral artery was ∼100 mm under isoflurane, but ∼75 mm under a-chloralose. The capillary diameter was observed to be larger under a-chloralose than isoflurane: 5.1 ± 1.2 mm vs. 4.8 ± 1.1 mm, respectively. A significant difference in the mean RBC speed measured in single capillaries was observed: 0.4 ± 0.4 mm/s under a-chloralose vs. 1.5 ± 0.4 mm/s under isoflurane. In agreement with these observations, arterio-venous transit-time and laser-Doppler flowmetry consistently showed a significant reduction of the RBC and plasma blood speed under a-chloralose relative to isoflurane. These findings may indicate that local blood flow regulatory mechanisms exist at the capillary level for the balance of oxygen supply and demand induced by anesthesia in the brain tissue. © Springer Science+Business Media, LLC 2010.