Chapter 27 Prevention of Glutamate Accumulation and Upregulation of Phospho-Akt may Account for Neuroprotection Afforded by Bergamot Essential Oil against Brain Injury Induced by Focal Cerebral Ischemia in Rat

The effects of bergamot essential oil (BEO; Citrus bergamia, Risso) on brain damage caused by permanent focal cerebral ischemia in rat were investigated. Administration of BEO (0.1-0.5 ml/kg but not 1 ml/kg, given intraperitoneally 1 h before occlusion of the middle cerebral artery, MCAo) significantly reduced infarct size after 24 h permanent MCAo. The most effective dose (0.5 ml/kg) resulted in a significant reduction of infarct extension throughout the brain, especially in the medial striatum and the motor cortex as revealed by TTC staining of tissue slices. Microdialysis experiments show that BEO (0.5 ml/kg) did not affect basal amino acid levels, whereas it significantly reduced excitatory amino acid, namely aspartate and glutamate, efflux in the frontoparietal cortex typically observed following MCAo. Western blotting experiments demonstrated that these early effects were associated, 24 h after permanent MCAo, to a significant increase in the phosphorylation and activity of the prosurvival kinase, Akt. Indeed, BEO significantly enhanced the phosphorylation of the deleterious downstream kinase, GSK-3β, whose activity is negatively regulated via phosphorylation by Akt.