The above image shows spontaneous changes in the intra-varicosity calcium concentration within a varicose sympathetic axon of the mouse vas deferens. In order to record these changes in calcium concentration, the varicosities were loaded with the calcium indicator Oregon Green 488 BAPTA-1 (Molecular Probes).
Images were captured every 216 ms using a Leica 4D laser scanning confocal microscope (NB: the movie may be playing at a faster rate than real time). The spontaneous activity is most prominent (in this recording) in the central varicosity.