Following the onset of an ischemic
brain injury, the excitatory
neurotransmitter glutamate is released. The excitotoxic effects of
glutamate are a major contributor to the pathogenesis of a
stroke. The aim of this study was to examine if overexpression of a
glutamate transporter (GLT-1) reduces ischemic
brain injury in a rat model of
stroke. We generated an adeno-associated viral (AAV) vector expressing the rat GLT-1
cDNA (AAV-GLT1). Functional expression of AAV-GLT1 was confirmed by increased
glutamate clearance rate in non-
stroke rat brain as measured by in vivo amperometry. AAV-GLT1 was injected into future cortical region of
infarction 3 weeks prior to 60 min
middle cerebral artery occlusion (MCAo). Tissue damage was assessed at one and two days after MCAo using TUNEL and TTC staining, respectively. Behavioral testing was performed at 2, 8 and 14 days post-
stroke. Animals receiving AAV-GLT1, compared to AAV-GFP, showed significant decreases in the duration and magnitude of extracellular
glutamate, measured by microdialysis, during the 60 minute MCAo. A significant reduction in
brain infarction and DNA fragmentation was observed in the region of AAV-GLT1 injection. Animals that received AAV-GLT1 showed significant improvement in behavioral recovery following
stroke compared to the AAV-GFP group. We demonstrate that focal overexpression of the
glutamate transporter, GLT-1, significantly reduces
ischemia-induced
glutamate overflow, decreases cell death and improves behavioral recovery. These data further support the role of
glutamate in the pathogenesis of ischemic damage in brain and demonstrate that targeted gene delivery to decrease the
ischemia-induced
glutamate overflow reduces the cellular and behavioral deficits caused by
stroke.