The hypothesis tying these three aims together is that the hundreds of molecules released by astrocytes, i.e. the astrocyte secretome affect the genotype, and therefore, the functional phenotype of various cells within the CNS, such as vascular endothelium responds to the astrocyte secretome by inducing new blood vessel formation. Furthermore, we find that exposure of the cerebral vasculature changes the phenotype in a manner which regulates cerebral blood flow (CBF) autoregulation (i.e. as blood pressure raises the capacity to regulate pressure-dependent myogenic tone such that blood flow is constant) is regulated in a circadian manner. Thus, blood flow autoregulation is at its lowest early in the morning and highest late at night when rat metabolic activity is within four hr of its highest level. It is interesting that stroke in most animals is at its greatest occurrence between 4 and 8 AM. Experiments are designed to determine if astrocytes act as a cellular pacemaker to modify myogenic activity and arterial pressure. Thus far, nearly all studies on astrocytes have been done in neonatal astrocytes. We provide data that astrocytes isolated and cultured from adults exhibit altered physiologic and phenotypic activity compared to those harvested from neonatal pups. To define differences in astrocyte secretome and the ability to change the genotype of neighboring cells in the CNS we will compare the astrocyte proteome from neonatal vs. adult to define the ability to alter the genotype of endothelial the cerebral circulation and vascular endothelium. Finally we will define the ability of neonatal and adult astrocyte proteome to affect the genome and function of invading tumor cells using a variety of techniques including: DNA microarray, intravital microscopy, continuous blood pressure recording of awake rats via 24 hr. telemetry as well as comparing changes in specific cellular signaling function. DNA analysis will be done using commercially available microchip arrays commercially available Arraystar microchips containing ~ 30,000 genes. The astrocyte proteome will be done using the Institutions Proteomic facility. Insight gained from such molecular/genetic data will provide novel clues in defining the function of neonatal and adult astrocytes, which exist together in the adult brain. We realize that, as written, each Specific Aim can stand alone. The common thread in the proposed approach is the specific ability to define the action of proteome from glial lineage aimed at matching blood flow to cerebral metabolic demand and dealing with cells which invade the brain. We have added two key personal to this grant to assist who have the prerequisite expertise to help ensure the completion of the Aims as outlined.