Abstract: As an energy dependent membrane transporter, P-GP expresses highly in the organs which have the function of barrier and secretory. In the brain, P-GP mainly expresses in the cerebral vascular endothelial cells of blood brain barrier .In the state of brain injury diseases (such as epilepsy and cerebral ischemia), P-GP appears in the hippocampus, cortex and striatum of rat brain. On a cellular level, it mainly exists in the cerebral vascular endothelial cells and also overexpresses in the neurons and glial cells.