Figure 2.

(A) Film autoradiogram of rat brain section 20 hours after the injection of [¹²⁵I]-BDNF (brain-derived neurotrophic factor) into the lateral ventricle (LV).¹² (B) Solute distribution into brain parenchyma from the cerebrospinal fluid (CSF) compartment is limited by the slow rate of solute diffusion from the ependymal surface, relative to the rapid rate of bulk flow (convection) of CSF from the ventricles to the systemic circulation across the arachnoid villi. (C) Logarithmic decrease in the brain concentration of glial-derived neurotrophic factor (GDNF) in the brain of the Rhesus monkey relative to the distance from the intracerebral catheter used for brain drug delivery with convection-enhanced diffusion.¹²⁷