The combination of patch-clamp and molecular biology techniques has made it possible to characterize the pharmacological and biophysical properties of ion channels in single neurons and to screen for expression of specific mRNAs in the same cell. Following whole-cell recording, the cytoplasm of the cell is harvested, and RNA is reverse transcribed into cDNA and amplified in PCR with primers specific for individual ion channel subunits. Additional experiments can then be designed to relate structure and function at the protein level more directly, since cells appear to regulate the composition of ion channels at least partly at the posttranscriptional stage.