GROWTH FACTORS INFLUENCE STROKE RECOVERY

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Recent data indicate that focal cerebral ischemia causes neural death, at least in part, through initiation of a "lethal cascade," which includes release of excitatory amino acids (EAAs) with consequent massive Ca2+ entry into cells, and resulting activation of intracellular proteases and nucleases, and generation of toxic free radicals and nitric oxide (NO). Basic fibroblast growth factor (bFGF) is a neuronotrophic polypeptide that promotes neuronal survival in vitro, and protects cultured neurons against a number of insults and toxins, including anoxia, hypoglycemia, EAAs, Ca2+ ionophore, free radicals, and NO. In preliminary studies, we found that exogenously-administered bFGF reduced infarct volume in models of focal cerebral ischemia in mature and neonatal rats in vivo. In the proposed studies, we will further explore the phenomenon and mechanism of bFGF neuroprotection in focal ischemia. These studies include: (1) further study of the dose, timing, and route of administration of bFGF in models of ischemia in mature and neonatal rats, as well as comparison of the effects of bFGF to other characterized growth factors, (2) studies of the biodistribution of exogenously- administered bFGF, and the density and localization of bFGF receptors after ischemia, (3) studies of regulation of candidate "neuroprotective" genes by exogenous bFGF, and (4) studies of the effects of bFGF on the cerebral vasculature. It is expected that these studies will shed new light on molecular mechanisms supporting neuronal survival after focal ischemia. P50NS108280032 This proposal utilizes a molecular genetics approach to generate and characterize animal models that lack the neuronal nitric oxide synthase (NOS) gene. Nitric oxide (NO) is a gas that is made by neurons, endothelial cells, glial cells, and other cells in the body. It has unusual properties that make it well suited to be a spatial messenger in cell-cell interactions. As a gas, it is freely diffusible across membranes. It binds to and is inactivated by heme, limiting its half- life to seconds. In the nervous system, NO has been implicated in establishing synaptic plasticity, in the physiologic and toxic response to excitatory neurotransmitters, and may play a role in ischemic damage from cerebrovascular disease. In the vasculature, NO is responsible for endothelial-derived relaxing factor (EDRF) activity, and is likely to be involved in resting blood vessel tone, as well as responses to vascular mediators and endothelial injury, in the cerebrovasculature as well as in the peripheral vasculature. We propose to develop and characterize mice in which the neuronal NOS gene has been selectively disrupted or "knocked-out," herein referred to as KN mice (knock-out, neuronal NOS). Ongoing work in our laboratory is devoted to the parallel development of mice in which the vascular NOS gene is knocked-out, KV mice (knock-out, vascular NOS). We propose to characterize the phenotype of the KN and KV mice, in terms of neuroanatomy and cerebral circulation. We hope to learn about the compensatory mechanisms that allow KN and KV mice to develop and survive in the absence of the endogenous neuronal and vascular NOS genes. This project will also maintain breeding colonies of KN and KV mice, in order to provide sufficient numbers of mice for project #1B. It is hoped that these experiments will contribute to our understanding of the molecular mechanisms involved in cerebrovascular tone in health and disease.