Spatial Buffering of K+ in Relation to Spreading Depression Models
Tony Gardner-Medwin
Physiology (NPP), University College London
G-M, COLES and TSACOPOULOS
Brain Research, 209 (1981) 452-457
K+ release from photoreceptors and uptake into glia in bee eye
[K+]o
[K+]i
(mM)
[K+]i
G-M, COLES and TSACOPOULOS
Brain Research, 209 (1981) 452-457
Spatial Buffer Mechanism: passive removal & transfer of e-c K+ through (mainly) astrocyte membranes & cytoplasm
Transfer Cells: (K+-selective)
Flux driven by a chemical gradient
Computational analysis
Flux driven by an electrical gradient
G-M (1983)J Physiol 335 393-426
Conclusions: SB flux ≈ 5x diffusion fluxSpace constant ≈ 0.2 mm (rat brain), 0.03 mm (frog brain)
G-M (1981)J. exp. Biol., 95, 111-127
K+ & Spreading Depression Instability theshold for K-induced K release
(Hodgkin, Grafstein, Tuckwell & Miura)Rapid K+ rise & recovery
in SD
G-M (1981)J. exp. Biol., 95, 111-127
SD (like the Migraine Aura) can be aborted by breathing O2+CO2
[Urethane anaesthetised rat]
Current patterns around the SD K+ disturbance
G-M (1992) in Spreading Depression, ed. RJ Do Carmo. Exp. Brain Res. Series 23,62-74
G-M, van Bruggen, Williams & Ahier (1994)J. Cerebral Blood Flow & Metabolism 14,7-11
Functional MRI : Propagation of SD waves in rat brain
[Regions of increased gradient echo (oxygenation sensitive) intensity superimposed on a spin echo image). Frame interval 12.2 s, after 150mM KCl application in a craniotomy chamber. Halothane anaesthetised rat, ]
MRI : the movie !
G-M, Tepley, Barkley, Moran, Nagel-Leiby, Simkins & Welch (1991) Brain Research 540, 153-158.
Slowly changing magnetic Signals from SD in rabbit brain
[Urethane anaesthetised rabbit]
G-M (1986) Ann NY Acad Sci, 481, 287-302
K+ load (mol/s/L
)
q
Complex Buffer Capacity: combining buffer mechanisms with different dynamics
G-M (1986) Ann NY Acad Sci, 481, 287-302
Buffering through netK+ uptake into cells
Buffering through diffusion in EC spaceand Spatial Buffering
Buffering Capacities relevant to preventing propagation of Spreading Depression