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Importance of glutamate‐generating metabolic pathways for memory consolidation in chicks
Author(s) -
Gibbs Marie E.,
Hertz Leif
Publication year - 2005
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.20548
Subject(s) - glutamate receptor , glycogenolysis , glutamine , chemistry , propranolol , memory consolidation , stimulation , neuroscience , biochemistry , medicine , endocrinology , biology , metabolism , amino acid , hippocampus , receptor
Glutamatergic and noradrenergic stimulation is essential for formation of memory of single‐trial discriminative avoidance of colored beads in the 1‐day‐old chick. Transmitter glutamate is released soon after training and again before memory consolidation 30 min after training. Memory consolidation is abolished by posttraining injection of iodoacetate, which inhibits glycolysis and thus not only energy metabolism but also pyruvate carboxylase‐dependent glucose conversion to glutamate, needed for consolidation; a similar effect is evoked by the antagonists propranolol acting at β 2 ‐adrenoceptors or SR59230A acting at β 3 ‐adrenoceptors. This paper shows that the effect of these inhibitors can be overcome by central injection of glutamine, providing an alternate source of transmitter glutamate and compensating for the inhibition of glycolysis by iodoacetate or the blockade of adrenergic stimulation of glycogenolysis by propranolol or of glucose uptake by SR59230A. Conversely, inhibition of memory consolidation by methionine sulfoximine (MSO), an inhibitor of glutamine synthetase and thus of the glutamate‐glutamine cycle, essential for neuronal reaccumulation of previously released transmitter glutamate, could be challenged by noradrenaline, stimulating glucose uptake and glycogenolysis and providing glutamate synthesis from glucose to compensate for the lack of return of previously released glutamate. Also, administration of either glutamine or noradrenaline could prevent the spontaneous decay of labile memory 30 min after training on a weakened stimulus, suggesting that direct supply of glutamate from glucose may secure sufficient supplies of transmitter glutamate for release prior to memory consolidation at 30 min. © 2005 Wiley‐Liss, Inc.