Delivering pharmacologic agents directly into the brain has been proposed as a means of bypassing the blood brain barrier.However,despite 16 years of research on a number of central nervous system disorders,an effective treatment using this strategy has only been observed in the brain tumor glioblastoma multiforme.Within this study we propose a novel system for delivering drugs into the brain named the simple diffusion (SDD) system.To validate this technique,rats were subjected to a single intracranial (at the caudate nucleus),or intraperitoneal injection,of the compound citicoline,followed two hours later by a permanent middle cerebral artery occlusion (pMCAO).Results showed that 12 h after pMCAO,with 0.0025 g kg-1 citicoline,an infarct volume 1/6 the size of the intraperitoneal group was achieved with a dose 1/800 of that required for the intraperitoneal group.These results suggest that given the appropriate injection point,through SDD a pharmacologically effective concentration of citicoline can be administered.