Combined Fluorometric and Electrophysiological Recordings

Combined electrophysiological and fluorometric recordings have proven to be a powerful tool, especially in the field of neurobiology. With this combination it became possible to overcome three major limitations of pure electrophysiological measurements. First, high-resolution recordings from cellular compartments distant to the recording electrode became feasible, allowing, for example, the quantification of the occupancy of postsynaptic receptors (Mainen et al., 1999 ) and the density of voltage-gated Ca²⁺ channels (Sabatini and Svoboda, 2000 ) at the level of single dendritic spines. Second, the analysis of cellular responses not directly associated with electrical signals became possible. Examples include synaptically evoked Ca²⁺ release from intracellular stores (Takechi et al., 1998 ; Finch and Augustine, 1998 ) and Ca²⁺ buffering by endogenous Ca²⁺ -binding proteins (Zhou and Neher, 1993 ). Third, the spatiotemporal extent of second messenger signals, for example, during subthreshold synaptic activity (Eilers et al., 1995a ) and during the induction of synaptic plasticity (Eilers et al., 1997b ), can be monitored by means of fluorescence imaging.