GCaMP6f indicates faster kinetics of astrocyte Ca²⁺ dynamics than GCaMP3.

<p>(<b>a</b>) Series of representative fluorescence images of astrocytes in layer 1 of primary visual cortex of an awake GLAST-CreER(+/-);R26-lsl-GCaMP6f(+/-) mouse. Image series covers one 5 s enforced locomotion event. (<b>b</b>) Black and gray traces represent time course of mean GCaMP3 or GCaMP6f fluorescence, respectively, from population of astrocytes as shown in a, in response to enforced locomotion (green bar). (<b>c</b>) Pseudocolored time course of GCaMP3 or GCaMP6f fluorescence in astrocytes in response to 6 consecutive trials of enforced locomotion (green bar). Flat magenta arrowheads indicate trials presented in b. Angled magenta arrowheads highlight prominent fluorescence transients in response to voluntary locomotion events. (<b>d</b>) Overlay of peak-aligned and normalized representative GCaMP3 (9 mice) or GCaMP6f (8 mice) fluorescence traces in response to enforced locomotion. (<b>e</b>) Overlay of peak-aligned and normalized fluorescence traces in response to enforced locomotion from astrocytes expressing GCaMP3 (black trace, 9 mice) or GCaMP6f (gray trace, 8 mice). (<b>f</b>) Same traces as in e, time-shifted to represent mean time from onset of enforced locomotion to peak (highlighted by dotted lines) of GCaMP3 (black trace) or GCaMP6f (gray trace) fluorescence. (<b>g</b>) Population data representing area under enforced locomotion-induced GCaMP fluorescence transient shown in e. a.u. represents seconds multiplied by normalized ΔF/F. Asterisk indicates p = 0.032 (unpaired t-test). Red lines represent mean ± SEM. (<b>h</b>) Population data representing time from onset of enforced locomotion to peak of GCaMP fluorescence shown in f. Asterisk indicates p = 0.017 (unpaired t-test). Red lines represent mean ± SEM. (i) Population data representing peak amplitudes of enforced locomotion-induced astrocyte GCaMP fluorescence transients. GCaMP3, 10 mice; GCaMP6f, 8 mice; n.s. indicates p = 0.813 (unpaired t-test). Red lines represent mean ± SEM.