From the study:
In neurons, glutamate retrieved from the cleft or provided by glutamine can be recycled as a neurotransmitter or used for oxidative metabolism. However, the uptake of glutamate is energy demanding. […] Increases in mitochondrial activity likely accompany high rates of neurotransmission to compensate for changes in metabolic demand. The regulation of mitochondrial metabolism may be particularly important in maintaining neurotransmission during exercise; however, studies investigating the adaptive role of mitochondria in the brain are scarce.