In the present work two different injection methods were used for transmission. For standard macroinjection, 30 μl of 1% brain homogenate was manually injected in the parietal region, and for microinjection, 1 μl of 10% brain homogenate was injected stereotactically into the striatum. Previously, we used the microinjection system to detect PrPSc in striatum as early as 30 min post-injection . Therefore, we reasoned that using the needle track wound as a guide in this transmission system, we might find PrPSc near the needle track at very early times and thus shorten the experiment. Unfortunately, this did not turn out to be the case, and even in the few microinjected mice which were positive (531dpi mice injected with G131V brain) the PrPSc was detected in the cortex and hippocampus rather than the striatum (Figs. 4 and 5). Therefore, the biological preference for another brain region appeared to overcome the fact that the injection was placed at a specific location in the striatum.