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Quantitative dual‐probe microdialysis: evaluation of [ 3 H]mannitol diffusion in agar and rat striatum
Author(s) -
Höistad Malin,
Chen Kevin C.,
Nicholson Charles,
Fuxe Kjell,
Kehr Jan
Publication year - 2002
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2002.00791.x
Subject(s) - microdialysis , mannitol , tortuosity , striatum , chemistry , diffusion , penetration (warfare) , interstitial space , extracellular , chromatography , biophysics , biochemistry , porosity , medicine , biology , pathology , thermodynamics , dopamine , physics , organic chemistry , operations research , engineering
Dual‐probe microdialysis was used to study interstitial diffusion in the rat brain. A radiolabelled tracer, [ 3 H]mannitol, was continuously infused at different concentrations via a probe acutely implanted into the striatum of an anaesthetized male rat or into a dilute agar gel. Samples were collected by a second probe placed 1 mm away from the first, and the recovered [ 3 H]mannitol was measured by liquid scintillation counting. In the striatum, the delivery of [ 3 H]mannitol was counteracted by its removal from the extracellular space by passive uptake into cells and clearance into the microcirculation, causing the diffusion profile to approach quasi steady‐state levels within 2 h. Diffusion data from brain and agar were analysed using a mathematical model. The apparent (effective) diffusion coefficient for [ 3 H]mannitol was D * = 2.9 × 10 −6 cm 2 /s, the effective volume fraction α* = 0.30 and the clearance rate constant κ = 2.3 × 10 −5 /s. A tortuosity, λ = 1.81, and penetration distance Γ = 4.2 mm, were calculated. We conclude that, using dual‐probe microdialysis, parameters reflecting geometric and dynamic tissue properties may be obtained using appropriate mathematical analysis. Quantitative dual‐probe microdialysis will be valuable in characterizing interstitial diffusion and the clearance processes underpinning volume transmission in the brain.