Fig. 2. Depolarization in high external K⁺ causes CBF excitation. (A) 30 mmol l^-1 K⁺ bath (filled circles) significantly increases CBF as compared to ASW controls (N=5, P0.0003) in CPE cell explants. After 3 min, 30 mmol l^-1 K⁺ is still excitatory (P0.02) but less so. After 6 min, 30 mmol l^-1 K⁺ is no longer excitatory. 30 mmol l^-1 K⁺ seawater was not excitatory in a zero Ca²⁺ bath (open squares, N=6), and only transiently so (P0.02) in a bath containing 50 µmol l^-1 of the Ca²⁺ channel blocker nifedipine (triangles, N=5). (B) 30 mmol l^-1 K⁺ significantly excites CBF in isolated, individual CPE cells (N=5, P0.007). ^*Significant change from mean basal levels.