Ca(2+) gradients within single mammalian CNS cells imaged by Quin 2 fluorescence.

Cells grown in culture from rat embryo diencephalon were loaded with the fluorescent calcium indicator Quin 2. Fluorescence from single cells in fields of 3 to 10 cells was imaged using a Charge Coupled Device (CCD) camera. Ratio images were produced by dividing intensities of individual pixels obtained by excitation at 340 nm (Ca-dependent) by the corresponding intensities obtained by excitation at 360 nm (isoemission with respect to Ca). Depolarizing solutions (high K, Ca) which should have promoted the entry of Ca into cells caused the ratio image to brighten in most cells examined (higher [Ca(2+)]). The Ca influx blockers nitrendipine and Cd dimmed the ratio image. Cells examined at early stages of development displayed active growth cones in which the ratio intensity was considerably higher than the cell body indicating Ca(2+) gradients on the order of 100 nm.