Regional Ki values in metastatic brain tumor-bearing animals. Quantitative increases in BTB permeability after biochemical modulation are shown in dose denpendent manner (A). Intravenous infusion of NS1619 (30 μg/kg/min; n = 5) significantly increased Ki in the tumor center compared with PBS control (p < 0.05). The optimal dose of NS1619 (60 μg/kg/min; n = 5) further increased Ki value (p < 0.01, NS1619 vs PBS). At higher dose (120 μg/kg/min; n = 6), however, no BTB permeability increased with infusion of NS1619. Intravenous infusion of BK (120 μg/kg/min; n = 3) also significantly increased Ki in the tumor center compared with control (p < 0.01). NS1619 (60 μg/kg/min)-induced BTB permeability increase was significantly attenuated by a specific KCa channels antagonist, IBTX (1 μg/kg/min; n = 4), (p < 0.05, NS1619+IBTX vs NS1619). While, intravenous infusion of IBTX (n = 3) alone did not show any effect on BTB permeability (B).