Leão's spreading depression is considered to be a humorally mediated reaction which can be evoked in different brain structures. Waves from either neocortex or striatum in rats may spread to the pyriform lobe, especially to the claustrum, amygdalar complex and pyriform cortex. The highest amplitude and the highest percentage of positive reactions were found in the claustrum and the lateral and basal nuclei of the amygdala. Because these structures represent the only reactive tissue connecting the neocortex and the corpus striatum it was concluded that the corticostriatal spreading depression transmission is realized through these areas. This assumption was confirmed by making cuts and electrolytical lesions in the above-mentioned structures, preventing the spreading depression transition in both directions. Minimal volume of reactive tissue (about 1mm³) is necessary for maintaining the spreading mechanism.