Chemically, lactic acid (LAc) is an alpha-hydroxy acid (AHA) due to the presence of carboxyl group adjacent to the hydroxyl group and therefore can undergo oxidation when challenged i.e. by oxidative potential. Voltammetry associated to micro-biosensors for selective and sensitive analysis of electrochemically active compounds is one of the main techniques of the modern scientific approach to study neuro-chemicals. Here this methodology was applied by means of differential pulse voltammetry associated with micro carbon fibre electrodes to attempt the in vitro as well as in vivo monitoring of LAc in the brain cortex of anaesthetized rodents. For this purpose, local treatment with exogenous LAc or systemic injection of sodium dichloroacetate (DCA) was performed in anaesthetized rodents. In addition, the influence of exogenous supply of oxygen (O₂) and carbon dioxide (CO₂) upon the basal levels of the putative LAc oxidation signal detected was studied.