DIFFERENCES IN STRIATAL EXTRACELLULAR AMINO-ACID-CONCENTRATIONS BETWEEN WISTAR AND FISCHER-344 RATS AFTER MIDDLE CEREBRAL-ARTERY OCCLUSION

We hypothesized that the interstrain difference between Wistar and Fis cher-344 (F344) rats in cerebral infarction volume after proximal midd le cerebral artery (MCA) occlusion might be explained by differences i n excitotoxicity between both rat strains. Using microdialysis we meas ured during a 5 h period after MCA occlusion the release of aspartate, glutamate and taurine in the cerebral cortex and the striatum. The vo lume of striatal infarction was comparable in Wistar and F344 rats. We found, however, in Wistar rats a significantly higher striatal efflux of aspartate and glutamate than in F344 rats, whereas the striatal ta urine efflux was of a similar magnitude in the two strains. Because of the (variably) smaller volume of cortical infarction in Wistar rats ( than that in F344), the location of the microdialysis probe-membrane w ith respect to the area of cortical infarction differed between Wistar rats. Hence, a reliable comparison between the quantitative amount of amino acids in the dialysate from the cortical probes of both rat str ains could not be made. These results, demonstrating differences in st riatal excitotoxicity between Wistar and F344 rats after MCA occlusion , are the first to show interstrain differences in striatal pathophysi ology of focal ischemia between these normotensive rat strains. They d o however not explain why MCA occlusion results in a significantly dif ferent volume of cortical infarction between Wistar and F344 rats. The F344 strain will probably show in a more sensitive way, as compared t o Wistar rats, neuroprotective effects of agents that diminish excitot oxic damage during focal cerebral ischemia.