“…This mechanistic view is supported by glutamine being preferentially metabolized to the transmitter pools of glutamate and GABA (Ward et al, 1983; Battaglioli and Martin, 1990; Sonnewald et al, 1993) in order to maintain increased neuronal activity (Szerb and O'Regan, 1985; Storm-Mathisen et al, 1986; Verderio et al, 1999; Holten and Gundersen, 2008). Furthermore, glutamine synthetase, the key enzyme catalyzing the formation of glutamine from glutamate, is localized to perisynaptic astroglial processes (Martínez-Hernandez et al, 1977), whereas phosphate-activated glutaminase (PAG) catalyzing regeneration of glutamate from glutamine is enriched in nerve terminals (Kvamme, 1983; Laake et al, 1999).…”