PMC:6194691 / 233115-234300 JSONTXT

{"target":"https://pubannotation.org/docs/sourcedb/PMC/sourceid/6194691","sourcedb":"PMC","sourceid":"6194691","source_url":"https://www.ncbi.nlm.nih.gov/pmc/6194691","text":"On closer inspection of Eq. 40 and the model on which it is based, the conversion factor in the third term, Vbr, is wrong (if the substance is restricted to the extracellular space, Vbr should simply be omitted [553]) but in addition there are more fundamental difficulties. The model is based on at least two unstated assumptions that limit its use: it is assumed that the only movement of ions through the cortex is via diffusion in the extracellular space and that there is no exchange of substance with CSF in the sub-arachnoid spaces. (The first of these shortcomings also compromises the analysis by Davson and Welch [417]). At least for K+ it is clear that movements within cell processes make an important contribution to movements within the cortex, so called spatial buffering (see e.g. [554–556]). As can be seen from Gardner-Medwin’s papers, if the tracer can enter and leave cells on the time scale of the experiments a proper description of the third term on the right hand side of Eq. 40 would be very complicated. The second assumption becomes important if perivascular clearance is comparable to the clearance across the blood–brain barrier (see end of this Appendix).","tracks":[]}