Microdomains that form on the plasma membrane of cells are essential for signalling compartmentation within cells. The localization of ion channels in these surface microdomains is important in defining what signalling cascades will be generated. For example, in cardiomyocytes, similar to other excitable cells, action potential propagation depends essentially on the properties of ion channels that are functionally and spatially coupled. In this chapter we describe a novel advanced patch-clamp technique, “Smart patch-clamp,” which enables the study of functional ion channels in the cell surface microdomains in a wide variety of biological cells and tissues. Smart patch-clamp combines conventional patch-clamp and Scanning Ion Conductance Microscopy (SICM). SICM uses a glass micropipette as scanning probe and generates a high-resolution topography image of the cell surface. Next, same micropipette is used as a patch-clamp pipette to record ion channel signals from specific spots on the cell surface as determined by SICM. In this chapter we focus on recording single channel L-type calcium channel currents from T-tubules of adult rat cardiomyocytes.
