Spatial flow-volume dissociation of the cerebral microcirculatory response to mild hypercapnia. Export

@article{citeulike:1095628, abstract = {The spatial and temporal response of the cerebral microcirculation to mild hypercapnia was investigated via two-photon laser-scanning microscopy. Cortical vessels, traversing the top 200 microm of somatosensory cortex, were visualized in alpha-chloralose-anesthetized Sprague-Dawley rats equipped with a cranial window. Intraluminal vessel diameters, transit times of fluorescent dextrans and red blood cells (RBC) velocities in individual capillaries were measured under normocapnic (PaCO2= 32.6 +/- 2.6 mm Hg) and slightly hypercapnic (PaCO2= 45 +/- 7 mm Hg) conditions. This gentle increase in PaCO2 was sufficient to produce robust and significant increases in both arterial and venous vessel diameters, concomitant to decreases in transit times of a bolus of dye from artery to venule (14\%, P < 0.05) and from artery to vein (27\%, P < 0.05). On the whole, capillaries exhibited a significant increase in diameter (16 +/- 33\%, P < 0.001, n = 393) and a substantial increase in RBC velocities (75 +/- 114\%, P < 0.001, n = 46) with hypercapnia. However, the response of the cerebral microvasculature to modest increases in PaCO2 was spatially heterogeneous. The maximal relative dilatation (range: 5-77\%; mean +/- SD: 25 +/- 34\%, P < 0.001, n = 271) occurred in the smallest capillaries (1.6 microm-4.0 microm resting diameter), while medium and larger capillaries (4.4 microm-6.8 microm resting diameter) showed no significant changes in diameter (P > 0.08, n = 122). In contrast, on average, RBC velocities increased less in the smaller capillaries (39 +/- 5\%, P < 0.002, n = 22) than in the medium and larger capillaries (107 +/- 142\%, P < 0.003, n = 24). Thus, the changes in capillary RBC velocities were spatially distinct from the observed volumetric changes and occurred to homogenize cerebral blood flow along capillaries of all diameters.}, address = {Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 10 Center Drive, Building 10, Room B1D114, Bethesda, MD 20892-1065, USA.}, author = {Hutchinson, E. B. and Stefanovic, B. and Koretsky, A. P. and Silva, A. C.}, citeulike-article-id = {1095628}, citeulike-linkout-0 = {http://dx.doi.org/10.1016/j.neuroimage.2006.03.033}, citeulike-linkout-1 = {http://view.ncbi.nlm.nih.gov/pubmed/16713717}, citeulike-linkout-2 = {http://www.hubmed.org/display.cgi?uids=16713717}, day = {15}, doi = {10.1016/j.neuroimage.2006.03.033}, issn = {1053-8119}, journal = {Neuroimage}, keywords = {anaesthesia, animal, bold, co2}, month = {August}, number = {2}, pages = {520--530}, posted-at = {2007-02-08 21:37:34}, priority = {2}, title = {Spatial flow-volume dissociation of the cerebral microcirculatory response to mild hypercapnia.}, url = {http://dx.doi.org/10.1016/j.neuroimage.2006.03.033}, volume = {32}, year = {2006} }

TY - JOUR ID - citeulike:1095628 L3 - citeulike-article-id:1095628 N2 - The spatial and temporal response of the cerebral microcirculation to mild hypercapnia was investigated via two-photon laser-scanning microscopy. Cortical vessels, traversing the top 200 microm of somatosensory cortex, were visualized in alpha-chloralose-anesthetized Sprague-Dawley rats equipped with a cranial window. Intraluminal vessel diameters, transit times of fluorescent dextrans and red blood cells (RBC) velocities in individual capillaries were measured under normocapnic (PaCO2= 32.6 +/- 2.6 mm Hg) and slightly hypercapnic (PaCO2= 45 +/- 7 mm Hg) conditions. This gentle increase in PaCO2 was sufficient to produce robust and significant increases in both arterial and venous vessel diameters, concomitant to decreases in transit times of a bolus of dye from artery to venule (14%, P < 0.05) and from artery to vein (27%, P < 0.05). On the whole, capillaries exhibited a significant increase in diameter (16 +/- 33%, P < 0.001, n = 393) and a substantial increase in RBC velocities (75 +/- 114%, P < 0.001, n = 46) with hypercapnia. However, the response of the cerebral microvasculature to modest increases in PaCO2 was spatially heterogeneous. The maximal relative dilatation (range: 5-77%; mean +/- SD: 25 +/- 34%, P < 0.001, n = 271) occurred in the smallest capillaries (1.6 microm-4.0 microm resting diameter), while medium and larger capillaries (4.4 microm-6.8 microm resting diameter) showed no significant changes in diameter (P > 0.08, n = 122). In contrast, on average, RBC velocities increased less in the smaller capillaries (39 +/- 5%, P < 0.002, n = 22) than in the medium and larger capillaries (107 +/- 142%, P < 0.003, n = 24). Thus, the changes in capillary RBC velocities were spatially distinct from the observed volumetric changes and occurred to homogenize cerebral blood flow along capillaries of all diameters. IS - 2 JF - Neuroimage SN - 1053-8119 AD - Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 10 Center Drive, Building 10, Room B1D114, Bethesda, MD 20892-1065, USA. EP - 530 TI - Spatial flow-volume dissociation of the cerebral microcirculatory response to mild hypercapnia. VL - 32 SP - 520 KW - anaesthesia KW - animal KW - bold KW - co2 AU - Hutchinson, EB AU - Stefanovic, B AU - Koretsky, AP AU - Silva, AC PY - 2006/08/15/ UR - http://dx.doi.org/10.1016/j.neuroimage.2006.03.033 ER -