Recently, it has been shown that brain topical superfusion of endothelin 1 (ET-1) at concentrations around 100 nM induces repetitive cortical spreading depressions (CSD) in vivo. It has remained unclear whether this effect of ET-1 is related to a primary neuronal/astroglial effect, such as increase in neuronal excitability or induction of interastroglial calcium waves, or a penumbra-like condition following vasoconstriction. In vitro, ET-1 regulates interastroglial communication via combined activation of ET_A and ET_B receptors, whereas it induces vasoconstriction via activation of ET_A receptors only. We have determined the ET receptor profile and intracellular signaling pathway of ET-1-induced CSD in vivo. In contrast to the ET_B receptor antagonist BQ-788 and concentration dependent, the ET_A receptor antagonist BQ-123 completely blocked the occurrence of ET-1-induced CSDs. The ET_B receptor antagonist did not increase the efficacy of the ET_A receptor antagonist. Direct stimulation of ET_B receptors with selective ET_B agonist BQ-3020 did not trigger CSDs. Phospholipase C (PLC) antagonist U-73122 inhibited CSD occurrence in contrast to proteinkinase C inhibitor Go-6983. Our findings indicate that ET-1 induces CSD through ET_A receptor and PLC activation. We conclude that induction of interastroglial calcium waves is unlikely the primary cause of ET-1-induced CSD. Based on the receptor profile, likely primary targets of ET-1 mediating CSD are either neurons or vascular smooth muscle cells.