StainingPO2 measurement sites in the rat brain cortex and quantitative morphometry of the surrounding capillaries

Abstract

The exact positions of microelectrodes used to measure the PO2 in the cerebral cortex of the rat were determined by staining the tissue with Alcian Blue. The measurement sites were subsequently located under a light microscope and correlated with the capillary and cellular arrangement of the cortex. The microelectrodes used for the PO2 measurements were made of gold glass fibers; the Alcian Blue was injected hydrostatically through a micropipette attached to the PO2 microelectrode. The sites where dye had been deposited were seen under a light microscope as green blue spots about 100 micrometers in diameter. The capillaries were visualized by silver nitrate perfusion. Differences between the local PO2 values in the neo- and the archeocortex were found. In the neocortex the mean PO2 was 31 mm Hg, capillary volume 1.6%, capillary surface area 980/mm2, capillary length 13.5/mm; whereas in the archeocortex these values where 21 mm Hg, 0.9%, 820/mm2 and 9.4/mm respectively. These data indicate a relationship between the microcirculatory transport system and the local oxygen tension and provide further evidence that the mean PO2 level tends to decrease when moving from the surface into the archeocortex.

Apparent diffusion time of oxygen from blood to tissue in rat cerebral cortex: implication for tissue oxygen dynamics during brain functions

“…This further supports the argument that oxygen diffusion in tissue is the dominant factor contributing to the phase difference in LCBF and PO 2 dynamics. Further studies are needed to determine the dependence of the diffusion time on the spatial proximity of the electrode tip to the nearest vessel and the type of the nearest vessel (arteriole, capillary, or venule) (28,47). Such studies will be possible with use of two-photon in vivo microscopic techniques, which allow direct simultaneous imaging of intracortical microcirculation and electrode positions (14,18).…”

Evaluation of the Permeation Characteristics of a Model Opioid Peptide, H-Tyr-d-Ala-Gly-Phe-d-Leu-OH (DADLE), and Its Cyclic Prodrugs across the Blood-Brain Barrier Using an In Situ Perfused Rat Brain Model

“…The samples were extracted with acetonitrile and analyzed using LC/MS/MS, as described under Materials and Methods. P app values were calculated from measured PA values based on the rat brain capillary surface area as reported by Metzer et al (1980). Results are the mean Ϯ S.D.…”

“…where F is the regional cerebral perfusion fluid flow, which was determined using [ 3 H]diazepam in separate experiments (0.025 ml/ s/g); P is the apparent permeability coefficient of the BBB for a test compound; and A is the rat brain capillary surface area (130 cm 2 /g), which was reported previously (Metzer et al, 1980). P was calculated by dividing PA by A.…”

A comparison of the effects of p-glycoprotein inhibitors on the blood–brain barrier permeation of cyclic prodrugs of an opioid peptide (DADLE)

“…The K in was determined by dividing the V br value by perfusion time. The K in values were converted to PA values using the Crone–Renkin model of capillary transfer:5 where F is the regional cerebral perfusion fluid flow, which was determined using [ 3 H]‐diazepam in separate experiments (0.025 mL/s/g);5 P is the apparent permeability coefficient of the BBB for a testing compound; and A is the rat brain capillary surface area (130 cm 2 /g), which was reported previously 18 . P was calculated by dividing PA by A .…”