Figure 7.

Heterogeneous types of calcium transients observed in ectopically labeled (Hb9⁻, GFP⁺/LacZ⁻) cells. A, Representative fluorescence traces of calcium transients seen in two types of ectopically labeled cells. Approximately half of the ectopically labeled cells showed large sawtooth-like calcium peaks during fictive locomotion, especially during fictive locomotion evoked by bath application of transmitters. The remaining half of the ectopically labeled cells were silent in all conditions tested. B, Magnified view shows that the sawtooth-like calcium peak onsets were not rhythmically coordinated to the phases of fictive locomotion (triangles if in phase with ipsilateral root activity, asterisks if out of phase). C, At higher transmitter concentrations, the frequency of occurrences of sawtooth-like calcium peak increased. Two ectopically labeled cells within the same imaging field of view showed calcium transients with distinctly different onset timing. D, Compared with Hb9⁺ interneurons, fewer ectopically labeled cells responded to electrical and/or chemical stimulations with calcium peaks. Population circular plot displaying only the responsive cells shows that most of them, including the ones exhibiting sawtooth-like calcium peaks, were not rhythmically active during chemical stimulation. contra., Contralateral; ipsi., ipsilateral.