Projection neurons of spinothalamic tract (STT) and postsynaptic dorsal column neurons (PSDC) convey information about nociceptive stimuli from the spinal cord level do higher brain centers. For detailed analysis of their properties it is possible to retrogradelly stain population of these neurons with fluorescent dyes (green color). Immunohistochemical techniques are used to study expression of different proteins (such as cFos) at differenty experimental conditions (red color).