increase ATP production and mitochondrial membrane potential without affecting cellular proliferation as well as the cytosolic and mitochondrial redox state in our experimental conditions. Furthermore, the increase of ATP production was in parallel to an improvement of the oxidative phosphorylation capacity of mitochondria, as indicated by an increase of the respiratory control ratio (RCR: mitochondrial respiratory state 3/state 4). We are currently investigating the effects of those neurosteroids on cellular antioxidant defences and on the expression of genes coding for mitochondrial proteins involved e.g. in the regulation of mitochondrial dynamics and apoptosis. Conclusion: Our first findings underscore the importance of neuroactive steroids as promising molecules able to improve cellular bioenergetics. Since each of them seems to have a specific action profile on bioenergetic outcomes, the underlying mechanisms still need to be elucidated in more detail.