Release of Endogenous Amino Acids from the Hippocampus and Brain Stem from Developing and Adult Mice in Ischemia |
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Authors: | Simo S Oja Pirjo Saransaari |
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Institution: | (1) Department of Paediatrics, Tampere University Hospital, Tampere, Finland;(2) Tampere Brain Research Center, Medical School, 33014 University of Tampere, Finland |
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Abstract: | The release of neurotransmitters and modulators has been studied mostly using labeled preloaded compounds. For several reasons,
however, the estimated release may not reliably reflect the release of endogenous compounds. The basal and K+-evoked release of the neuroactive endogenous amino acids GABA, glycine, taurine, l-glutamate and l-aspartate was now studied in slices from the hippocampus and brain stem from 7-day-old and 3-month-old mice under control
and ischemic conditions. The release of synaptically not active l-glutamine, l-alanine, l-threonine and l-serine was assessed for comparison. The estimates for the hippocampus and brainstem were markedly different and also different
in developing and adult mice. GABA release was much greater in 3-month-old than in 7-day-old mice, whereas with taurine the
situation was the opposite, in the hippocampus in particular. K+ stimulation enhanced glycine release more in the mature than immature brain stem while in the hippocampus the converse was
observed. Ischemia enhanced the release of all neuroactive amino acids in both brain regions, the effects being relatively
most pronounced in the case of GABA, aspartate and glutamate in the hippocampus in 3-month-old mice, and taurine in 7-day-old
and glycine in 3-month-old mice in the brain stem. These results are qualitatively similar to those obtained on earlier experiments
with labeled preloaded amino acids. However, the magnitudes of the release cannot be quite correctly estimated using radioactive
labels. In developing mice only taurine release may counteract the harmful effects of excitatory amino acids in ischemia in
both hippocampus and brain stem. |
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Keywords: | Amino acid release Endogenous amino acids Ischemia Hippocampus Brain stem Tissue slices Adult and developing mice |
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