The measurement of changes in intracellular free calcium during action potentials in mammalian neurones.

This report describes the techniques we have developed to record changes in intracellular calcium concentration which take place during action potentials in the cell body of rat dorsal root ganglion neurones in vitro. The photoprotein, aequorin, was microinjected into the cell body of individual sensory neurones and light output from Ca2+-activated aequorin molecules was recorded with a photomultiplier tube attached to a modified inverted microscope. Aspects of the technology outlined here include: cell culture methods; a flow chamber for electrophysiological experiments on cell culture preparations; modifications to our inverted microscope; use of 150 mM KCl-filled microelectrodes; and an electronic device for processing the photomultiplier output. Some preliminary results are presented.