Uncaging Calcium in Neurons
Changes in intracellular free calcium concentration (Δ[Ca 2+ ] i ) driving physiological events such as neurotransmitter release or Ca 2+ -dependent currents can be monitored using Ca 2+ -sensitive fluorescent dyes. Although these dyes can correlate Δ[Ca 2+ ] i with a physiological event, they cannot directly test for causality between changes in [Ca 2+ ] i and that event. Photolabile Ca 2+ chelators are Ca 2+ -binding molecules that can alter and, to a certain extent, control [Ca 2+ ] i in an inducible manner and with temporal and spatial resolution that surpasses microinjection or ionophore application. Here we discuss the properties of caged Ca 2+ compounds as well as some practical considerations for their use in neuronal cells, where they have proven particularly effective.