There are provided a compound for treatment or prevention of brain injury caused by diseases such as cerebrovascular disorder and brain degenerative disease and demyelinating disease and a method for screening the same. Brain injury in which prostaglandin D2 is participated is treated or prevented by inhibition of hematopoietic prostaglandin D synthase induced in microglia cell or macrophage of brain injury area by diseases such as cerebrovascular disorder and brain degenerative disease or demyelinating disease or by inhibition of activation of prostaglandin D receptor expressed in astroglia cell around the injured area. There is also provided a method of testing those pharmaceutical substances using a transgenic mouse in which human hematopoietic prostaglandin D synthase is expressed in large amounts.
