To determine if the above changes resulted from PI3K activation, mice were treated with the PI3K inhibitor LY294002 (5 nM in 1 μL i.c.v.) 90 min prior to d-fenfluramine treatment. LY294002 moderately reduced the d-fenfluramine-induced increases in phospho-Thr308-Akt and phospho-Ser473-Akt in both cerebral cortex and hippocampus. It also reduced d-fenfluramine-induced increases in phospho-Ser256-FoxO1 and phospho-Ser253-FoxO3a, with the effect significant in the cerebral cortex and moderate in the hippocampus (Figure 2c and Table 1). The above results suggest that increasing brain serotonergic activity by d-fenfluramine activates Akt at least partially via PI3K to phosphorylate and inactivate FoxO transcription factors in the mouse brain.
