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Acidic Amino Acid Clearance from CSF in the Neonatal Versus Adult Rat Using Ventriculo‐Cisternal Perfusion
Author(s) -
AlSarraf Hameed,
Preston Jane E.,
Segal Malcolm B.
Publication year - 2000
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2000.740770.x
Subject(s) - amino acid , glutamate receptor , perfusion , medicine , endocrinology , clearance rate , metabolism , biology , chemistry , biochemistry , receptor
The acidic amino acids aspartate and glutamate are excitatory neurotransmitters in the CNS. The clearance of this group of amino acids from CSF of adult and neonatal (7‐day‐old) rats was investigated. Ventriculo‐cisternal perfusions with 14 C‐amino acids and 3 H‐dextran were carried out for up to 90 min. Uptake of the amino acids by the whole brain was measured, and the loss to blood was calculated. 3 H‐Dextran was included in the perfusate for measurement of CSF secretion rate. After 90‐min perfusion, both aspartate and glutamate showed a similar uptake into the whole brain, and this did not change with age ( p > 0.05). However, clearance from CSF was greater in the adult, as was entry into blood from CSF. Addition of 5 m M excess unlabelled amino acid resulted in reduction in the brain uptake of both 14 C‐amino acids in the adult rat. In the neonate, addition of aspartate also reduced brain aspartate uptake, whereas addition of glutamate increased brain neonatal [ 14 C]glutamate uptake. The rate of CSF secretion was significantly greater in the adult, 1.26 ± 0.18 μl · min ‐1 · g ‐1 , than in the neonate, 0.62 ± 0.08 μl · min ‐1 · g ‐1 , and the turnover of CSF was greater in adults ( p < 0.01). In summary, both aspartate and glutamate showed greater clearances from CSF in the adult than the neonate. This clearance was found to be by carrier‐mediated mechanisms.