To confirm functional expression of KCa3.1 K+ channels in the plasma membrane of SMA-540 murine glioma cells and to identify its dependence on the culture conditions, macroscopic on-cell (cell-attached) currents as obtained with patch-clamp recordings in voltage-clamp mode were compared between cells grown in NSC medium and continuously DMEM medium-cultured sub-confluent monolayers. Here, KCNN4 is linked to central nervous system cancer.