Concentrations measured in CSF are, with the exception of glutamine always substantially less, than the concentrations in plasma. Concentrations in ISF are measured by microdialysis with extrapolation to zero flow (see text). If these are correct, ISF concentrations are substantially lower than those in CSF. c cisternal, l lumbar 1Plum et al. [576] 2Franklin et al. [577] 3McGale et al. [578] 4Hamberger et al. [579] 5Lerma et al. [580] 6Dolgodilina et al. [581] 7Table 8.15 in Davson and Segal [56] 8Jacobson et al. [582] microdialysis by concentration profile 9Jacobson et al. [582] microdialysis by recovery of samples