Creatine supplementation is in widespread use to enhance sports-fitness performance, and has been trialled successfully in the treatment of neurological, neuromuscular and atherosclerotic disease. Creatine plays a pivotal role in brain energy homeostasis, being a temporal and spatial buffer for cytosolic and mitochondrial pools of the cellular energy currency, adenosine triphosphate and its regulator, adenosine diphosphate. In this work, we tested the hypothesis that oral creatine supplementation (5 g d 2 1 for six weeks) would enhance intelligence test scores and working memory performance in 45 young adult, vegetarian subjects in a double-blind, placebo-controlled, cross-over design. Creatine supplementation had a significant positive effect ( p , 0.0001) on both working memory (backward digit span) and intelligence (Raven's Advanced Progressive Matrices), both tasks that require speed of processing. These findings underline a dynamic and significant role of brain energy capacity in influencing brain performance.

The role of glutamine and alanine transport in the recycling of neurotransmitter glutamate was investigated in Guinea pig brain cortical tissue slices and prisms, and in cultured neuroblastoma and astrocyte cell lines. The ability of exogenous (2 mM) glutamine to displace 13 C label sup-13 C]glucose was investigated using NMR spectroscopy.Glutamine transport was inhibited in slices under quiescent or depolarising conditions using histidine, which shares most transport routes with glutamine, or 2-(methylamino)isobutyric acid (MeAIB), a specific inhibitor of the neuronal system A. Glutamine mainly entered a large, slow turnover pool, probably located in neurons, which did not interact with the glutamate/glutamine neurotransmitter cycle. Abbreviations used: ASCT-2, system ASC amino acid transporter; ATA1 and ATA2, system A amino acid transporters; EAAT, excitatory amino acid transporter; HBSS, HEPES-buffered salt solution; MeAIB, 2-(methylamino)isobutyric acid; RPMI, Roswell Park Memorial Institute Medium 1640.