DIFFUSION HETEROGENEITY AND ANISOTROPY IN RAT HIPPOCAMPUS

WE provide evidence for anisotropic diffusion in rat corpus callosum a nd hippocampus. The preferential diffusion pathway in corpus callosum is along the myelinated axon fibres; in the hippocampus diffusion is e asier along the transversal axis (x) than along the sagittal (y) or ve rtical (z) axes. In all areas studied, i.e. in the cortex, corpus call osum and hippocampus, the mean ECS volume fraction alpha (alpha = ECS volume/total tissue volume) ranged between 0.20 and 0.22 and mean non- specific uptake k' was between 4.0 and 5.9 x 10(-3) s(-1). Diffusional anisotropy in the hippocampus may be of importance for extrasynaptic transmission and in the 'cross-talk' between synapses. (C) 1998 Rapid Science Ltd.