Drugs intended to increase wellness or quality of life ("lifestyle drugs") have gained popularity and/or importance over recent years. Biogenic substances like nicotinamide adenine dinucleotide (NADH) are supposed to increase the physical and intellectual performance without side-effects. NADH is an energy-delivering co-substrate in the respiratory chain. Clinical studies showed positive effects of peripherally given NADH in Morbus Parkinson and major depression. NADH can be measured by its fluorescence. In this study a pulsed N2-laser combined with a fibre-optic probe and photomultipliers was used to induce and measure NADH fluorescence in the rat cortex. The aims of the study were to assess the suitability of the laser-induced spectroscopy for in vivo and on-line measurement of NADH in neuroscience and the assessment of the central availability of NADH after peripheral administration. NADH (50 mg/kg) but not the precursor nicotinamide caused a significant rise of the NADH fluorescence intensity indicating an increase of the NADH concentration in the rat cortex. In conclusion, the results suggest that NADH given orally or intraperitoneally increases the amounts of NADH in the brain. The results may thus help to explain the clinical effects reported.