Influence of nicotine upon human brain metabolism, an in vivo noninvasive Near Infrared Spectroscopy (NIRS) study

Nicotine, a natural alkaloid derived from tobacco, is involved in various outcomes ranging from addiction to toxicity and/or neuro-protective actions. Nevertheless, the literature on the effects of nicotine administration upon the activity of brain regions is mixed; either increased, decreased, or no overall effect was reported when being evaluated by various methodologies such as positron emission tomography (PET), functional Magnetic Resonance Imaging (fMRI). In this work, Near Infrared Spectroscopy (NIRS) is applied as it allows monitoring oxygen saturation in the living tissue as well as changes in oxygenation of hemoglobin and when applied on brain studies, it gives indications of cerebral haemo-dynamics as well as brain metabolism. In particular, here NIRS has been applied in human volunteers as this methodology is based upon the use of harmless radiations so that to provide a non-invasive, non-ionizing procedure to monitor 2 main forms of hae­moglobin: oxy-haemoglobin (HbO2) and deoxy-haemoglobin (Hb). The data gathered indicate an overall positive influence of nicotine upon HbO2 levels, as well as total blood volume (V) therefore suggesting an increased brain metabolism. Finally these data further propose NIRS with its characteristics of noninvasiveness, easy to-use, portable, restraint-free therefore relatively psychologically undemanding, as replicable and ideal methodology for clinical applications and translational approaches.