Capillary level imaging of local cerebral blood flow in bicuculline-induced epileptic foci
Section snippets
Subjects and surgery
Male and female C57BL6 mice (20 g–30 g) were used. Animals were deeply anesthetized with either urethane (1.7 g/kg) or ketamine–xylazine cocktail (25 mg ketamine, 6.3 mg xylazine, 0.25 mg acepromazine per 1.0 ml solution, cocktail dosage=3 ml/kg). Two small stainless micro-screws were driven into the bone above the cerebellum. These screws serve as the ground and reference electrodes for the differential recording of local field potential. An insulated metallic head frame (approximately 1 cm×4 cm,
Visualization and measurement of capillary level hemodynamics
Blood flow was imaged and quantified in a total of 163 capillaries from 26 animals. This included eight animals under urethane anesthesia and 18 animals under ketamine–xylazine anesthesia. Among the ketamine–xylazine-anesthetized population, IISs were induced in 12 animals. Microvessels that had the inner diameter (i.e. FITC filled portion) of less than or equal to 6 μm are considered to be capillaries.
Capillary blood flow can be quantified in terms of the flux (number of traveling RBCs per unit
Discussion
Two-photon imaging of capillaries filled with fluorescently labeled serum yields the highest time and spatial resolution of blood flow among currently available techniques for blood flow measurements. We have utilized 2-PLSM to investigate capillary level blood flow in layer II/III of the somatosensory cortex in both basal conditions and bicuculline-induced epileptic conditions. As a result, we found a reliable relationship between activity changes of neurons and intracortical blood
Acknowledgments
We thank A. G. Hudetz, D. L. Buhl, and A. Sirota for their critical comments on an earlier version of this manuscript. This work was supported by National Institutes of Health grant NS043157 (G.B.) and by the Epilepsy Foundation (H.H.).
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