|Title||Simultaneous sodium and calcium imaging from dendrites and axons
|Author||Kenichi Miyazaki, William N. Ross
|Affiliation(s)||Department of Physiology, New York Medical College, Valhalla, NY 10595 and Marine Biological Laboratory, Woods Hole, MA 02543
|Published|| eNeuro 2015 DOI: 10.1523/ENEURO.0092-15.2015
|Keyword||calcium, imaging, sodium, Ca, Na, in-vitro
|Abstract||Dynamic calcium imaging is a major technique of neuroscientists. It can reveal information
about the location of various calcium channels and calcium permeable receptors, the time
course, magnitude, and location of intracellular calcium concentration ([Ca2+ 31 ]i) changes, and
indirectly, the occurrence of action potentials. Dynamic sodium imaging, a less exploited
technique, can reveal analogous information related to sodium signaling. In some cases, like the
examination of AMPA and NMDA receptor signaling, measurements of both [Ca2+]i and [Na+ 34 ]i
changes in the same preparation may provide more information than separate measurements.
To this end we developed a technique to simultaneously measure both signals at high speed
and sufficient sensitivity to detect localized physiological events. This approach has advantages
over sequential imaging since the preparation may not respond identically in different trials.
We designed custom dichroic and emission filters to allow the separate detection of the
fluorescence of sodium and calcium indicators loaded together into a single neuron in a brain
slice from the hippocampus of Sprague Dawley rats. We then used high intensity light emitting
diodes (LEDs) to alternately excite the two indicators at the appropriate wavelengths. These
pulses were synchronized with the frames of a CCD camera running at 500 Hz. Software then
separated the data streams to provide independent sodium and calcium signals. With this
system we could detect [Ca2+]i and [Na+]i changes from single action potentials in axons and
synaptically evoked signals in dendrites, both with submicron resolution and a good signal to
noise ratio (S/N).