NAA and NAAG variation in neuronal activation during visual stimulation

Autor(es)

Castellano, G. ^[1] ; Dias, C. S. B. ^[1] ; Foerster, B. ^[2] ; Li, L. M. ^[3] ; Covolan, R. J. M. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, Inst Fis Gleb Wataghin, Dept Raios Cosmicos & Cronol, Grp Neurofis, Campinas, SP - Brazil

^[2] Philips Med Syst, Sao Paulo, SP - Brazil

^[3] Univ Estadual Campinas, Fac Ciencias Med, Dept Neurol, Campinas, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Brazilian Journal of Medical and Biological Research; v. 45, n. 11, p. 1031-1036, NOV 2012.
• Citações Web of Science: 11

Resumo

N-acetyl-aspartyl-glutamate (NAAG) and its hydrolysis product N-acetyl-aspartate (NAA) are among the most important brain metabolites. NAA is a marker of neuron integrity and viability, while NAAG modulates glutamate release and may have a role in neuroprotection and synaptic plasticity. Investigating on a quantitative basis the role of these metabolites in brain metabolism in vivo by magnetic resonance spectroscopy (MRS) is a major challenge since the main signals of NAA and NAAG largely overlap. This is a preliminary study in which we evaluated NAA and NAAG changes during a visual stimulation experiment using functional MRS. The paradigm used consisted of a rest period (5 min and 20 s), followed by a stimulation period (10 min and 40 s) and another rest period (10 min and 40 s). MRS from 17 healthy subjects were acquired at 3T with TR/TE = 2000/288 ms. Spectra were averaged over subjects and quantified with LCModel. The main outcomes were that NAA concentration decreased by about 20% with the stimulus, while the concentration of NAAG concomitantly increased by about 200%. Such variations fall into models for the energy metabolism underlying neuronal activation that point to NAAG as being responsible for the hyperemic vascular response that causes the BOLD signal. They also agree with the fact that NAAG and NAA are present in the brain at a ratio of about 1: 10, and with the fact that the only known metabolic pathway for NAAG synthesis is from NAA and glutamate. (AU)

• Processo FAPESP: 08/02246-9 - Aplicação combinada das técnicas de espectroscopia de MR dinâmica e EEG para o estudo do metabolismo cerebral subjacente à atividade de espículas em pacientes epilépticos
• Beneficiário: Carlos Sato Baraldi Dias
• Modalidade de apoio: Bolsas no Brasil - Mestrado
• Processo FAPESP: 05/56578-4 - Centro multimodal de neuroimagens para estudos em epilepsia
• Beneficiário: Fernando Cendes
• Modalidade de apoio: Auxílio à Pesquisa - Programa CINAPCE - Temático
• Processo FAPESP: 09/10046-2 - Espectroscopia Funcional por Ressonância Magnética (fMRS)
• Beneficiário: Gabriela Castellano
• Modalidade de apoio: Auxílio à Pesquisa - Regular