P2X7 receptor is a member of the P2X family of ATP-gated ion channels. The cellular localization of P2X7 receptors in the central nervous system remains controversial because immunohistochemical staining patterns are inconsistent among antibodies. Here we examined the precise distribution of P2X7 mRNAs in the rat brain using isotopic in situ hybridization. P2X7-positive glial-like small cells were sporadically scattered in almost all areas of the brain. P2X7-positive glial-like small cells were also observed in nerve fiber tracts such as the anterior commissure, corpus callosum (CC), optic tract, and internal capsule. P2X7-positive neurons were found in the anterior olfactory nucleus, cerebral cortex, piriform cortex (Pir), lateral septal nucleus (LS), hippocampal pyramidal cell layers of CA1, CA3, CA4, pontine nuclei, external cuneate nucleus, and medial vestibular nucleus. P2X7 hybridization signals were also observed in the motor neurons of the trigeminal motor nucleus, facial nucleus, hypoglossal nucleus, and the anterior horn of the spinal cord. P2X7 mRNA was expressed in the ependymal cells around the olfactory ventricle, lateral ventricles (LV), third ventricle (3V), cerebral aqueduct (Aq), fourth ventricle (4V), and central canal. The P2X7 hybridization signal was also very strong in the area postrema (AP). The double staining experiments demonstrate that neurons, oligodendrocytes, and microglia expressed P2X7 receptor mRNAs. These findings suggest that P2X7 receptors may play a variety of roles in a wide range of cell types in the brain.