EDN1 and Anxiety: To further test the above conclusion that the ET1-ETBR contributes regulating anxiety, we used an shRNA lentivirus-mediated gene knock-down technique and compared the effect of treatment with LV-ETBR shRNA (0.25 μl) + LV-ET1 shRNA (0.25 μl) with that of treatment with LV-ETBR shRNA (0.5 μl) alone.