Direct Identification of Electrophysiologically Monitored Cells Within Intact Mouse Islets of Langerhans

Cells found to be electrically active within microdis-sected mouse islets of Langerhans perifused with high (≥11.1 mM) glucose concentrations were labeled by injecting Lucifer yellow through the recording electrode. After fixation, these cells were located by fluorescence microscopy on sections serially cut throughout the islets and were subsequently identified by immunofluor-orescence staining with specific anti-islet hormone sera. Electrophysiologic control confirmed that the electrode tip had remained within the same cell throughout the experiment and showed that Lucifer yellow labeling did not affect the electrical activity of the impaled cell. Upon individual impalements, Lucifer yellow labeled either the impaled cell alone or this cell and some of its neighbors to which it was dye coupled. Immunofluorescence staining of the Lucifer yellow-labeled cells revealed that glucose-induced electrical activity was recorded from individual B-cells or groups of dye-coupled B-cells as well as from A-cells coupled to B-cellS.