Translocator protein 18 kDa, the peripheral benzodiazepine receptor by its earlier name, is a mitochondrial membrane protein associated with the mitochondrial permeability pore. While the function of the protein is not properly understood, it is known to play roles in necrotic and apoptotic processes of the neural tissue. In the healthy adult brain, TSPO expression is restricted to glial cells. In developing or damaged neural regions, however, TSPO appears in differentiating/regenerating neurons. Using immunocytochemical, molecular biological and cell biological techniques, we demonstrate that TSPO mRNA and protein, while missing from mature neurons, are present in neural stem cells and also in postmitotic neuronal precursors. Investigating some distinct stages of in vitro differentiation of NE-4C neural stem cells, TSPO 18 kDa was found to be repressed in a relatively late phase of neuron formation, when mature neuron-specific features appear. This timing indicates that mitochondria in fully developed neurons display specific characteristics and provides an additional marker for characterising neuronal differentiation.