EVALUATION OF MONOAMINERGIC NEUROTRANSMITTERS IN THE ACUTE FOCAL ISCHEMIC HUMAN BRAIN MODEL BY INTRACEREBRAL IN-VIVO MICRODIALYSIS

The release of neurotransmitters principally glutamate during cerebral ischemia has been extensively studied, It is well recognized that isc hemia induced release of glutamate plays a key role in ''excitotoxic'' neuronal death, The role of monoaminergic neurotransmitters is howeve r unclear. The purpose of this study was to evaluate the extracellular norepinephrine, 3,4-dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindo leacetic acid (5-HIAA) and serotonin (5-HT) under varied degrees of is chemia in the acute focal ischemic model of the human brain by in-vivo microdialysis. The ischemic response of these amines was correlated w ith the glutamate levels. Our study concludes that these amines and me tabolites can be detected in the human ''stroke'' model. No marked flu ctuations were noted in the levels of norepinephrine and DOPAC. Howeve r, significant changes to partial and total ischemia were noted in the extracellular levels of 5-HIAA and 5-HT. These compounds showed a dra matic increase with the onset of ischemia with higher detectable level s in the partial ischemic state in comparison to the total ischemic di alysate levels. The exact role played by the differential increase in the levels of 5-HT to the other catecholamines in the pathogenesis of ischemic neuronal damage remains unclear and warrants further study.