The functional activity of ion channels is affected by their local environment, and for certain types of channels this local effect is critical. This chapter describes a method of recording the activity of ATP-sensitive K⁺ channels, expressed on the plasma membrane of pancreatic β-cells, without destroying the β-cell architecture. In the open-cell cell-attached patch-clamp configuration, ligands and effectors of these metabolism-dependent channels are delivered to their cytoplasmic side via pores in the plasma membrane produced by bacterial toxins.