Tissue plasma volume was determined by measured radioactivity of 125I, which represents radioactivity from only plasma. Leakage of infused radioactive albumin during the 3 min of its circulation time must be regarded as insignificant, and has been analysed before [35]. This means that the calculated increase in plasma volume, most likely, was an effect of inflammatory-induced vasodilation rather than extravasation. In addition, we observed no changes in brain water content which illustrates that there is not a large extravasation of water and that the intracranial pressure is maintained after the addition of either of the inflammatory substances. It is worth noting that an increase in plasma volumes after application of CFA and IS may affect the calculations of PS, especially in areas with low permeability for [51Cr]-EDTA in terms of in underestimation of PS (Ki), as B is indirectly dependent on plasma volume (see Methods), The theory behind the present method has been discussed before, see Chodobski and colleagues [14].