You might find this chapter interesting, http://papers.cnl.salk.edu/PDFs/Extracellular%20Potassium%20Dynamics%20and%20Epileptogenesis%202008-4094.pdf

Thanks for your reply Deepak. I have been through this before and it is indeed interesting. However, they only talk about 'transient increase in Ko' or 'slow modulation of Ko' , without mentioning the exact time delay value with respect to neural firing.

Also, I am not very clear with the fact that it is the high value of Ko that is characteristic of seizures or large variations in Ko that are seen during seizures?

Karishma, Fig 26.2B shows changes in [K+]o over time with neuronal firing,although these were evoked, not spontaneous. Spontaneous bursts under "physiological conditions" have been shown to elevate [K+]o by 0.2mM, but the increase in [K+]o differs with different neurons. (Somjen G. G. 1979; http://www.annualreviews.org/doi/abs/10.1146/annurev.ph.41.030179.001111).

That said, you might find this paper by Santhakumar et al., (http://www.ncbi.nlm.nih.gov/pubmed/12843291) interesting in terms of rise and latency of [K+]o after single pulse stimulation in Dentage gyrus.

From what I know, whether changes in [K+]o are a cause or an effect of seizures still seems to be debated. However, an increase in [K+]o during the tonic phase of seizure and a gradual decrease during clonic phase of a seizure have been shown both under invivo and invitro conditions. (see Fröhlich F et al 2008 ; http://www.ncbi.nlm.nih.gov/pubmed/18997121).

Hope this helps.

From mi experience in vitro K starts to rise within 1s after the onset of neuronal discharge evoked with 10Hz stimulation. but this delay could be an artefact of the K-sensitive electrode latency. BR

Thanks again Deepak. Interesting references-all of them. However, I am not really convinced with 0.2 mM (seems to be high for spontaneous bursts). Anyways I will study more about it. :)

@Anton Ivanov

Thanks for your reply. Its certainly useful information (in the modelling perspective). I would really appreciate if you could send me some reference for the same. Besides, I am wondering 1 sec isnt high enough for being an artifact , while we consider neuronal firing on the scale of milliseconds??

Our group has recently published a modeling paper on this, in particular in the role of astrocytes in buffering it away. Maybe it can be of help?http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.1003386 Best regards Gaute

Not sure this will help but I remember a 1987 Journal of Neurophysiology paper by Pitler and Landfield in which they recorded from a presumed glial cell in the hippocampal slice during 10 Hz synaptic activation. The depolarization and time where quantified so I think the info you are looking for may be in that paper but it took 20-30 sec to get mac depolarization in the putative glial cell.

Dear Gaute Einevoll,

Thanks for the reference. I am reading the paper, it seems really interesting, pretty extensive and insightful modelling work. Not specifically related to my work but definitely insightful regarding the buffering action of buffering. One noteworthy point in the paper, glial buffering action occurs on the scale >1 sec, while diffusion effects at the time scale of

Dear Oliver Thibault,

Thanks for the reference. Just to confirm, is this the one:

Landfield PW (1987) “Increased calcium current” hypothesis of brain ag-

ing. Neurobiol Aging 8:346 –347 ??

Dear Karishma; Thanks for the nice words about our paper. I think both glial processes and 'longitudinal' diffusion (meaning diffusion along the long axis of the neuron/ECS/astrocyte) typically are quite slow processes (> 100 ms). The fast millisecond processes in the neuron (such as the action potential) are due to fast transport processes across the membrane which both have electrical drift and diffusive contributions. Best regards Gaute

extracellular potassium accumulation is modelled as part of the paper:

The Sodium-Potassium Pump Controls the Intrinsic Firing of the Cerebellar Purkinje Neuron

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0051169