Figure 2. Depolarization evokes reproducible GCaMP3 signals in vitro.
(A) Application of 50 mM K+ produced a robust fluorescent signal in the vast majority of dissociated DRG neurons, and peak evoked fluorescence (F–F0) expressed as a% of the initial K+ application significantly decreased with subsequent applications. Data are presented as mean ± SEM. *p<0.001 versus K+ #1; #p<0.0001 versus K+ #2. (B) The time to decay to 50% of peak signal (T50) following K+-evoked depolarization also significantly decreased with repeated application of K+. Data are presented as mean ± SEM. *p<0.0001. (C) Distribution of somata diameter of cultured DRG neurons that did (light gray bars) and did not (dark gray bars) exhibit an increase in GCaMP3 signal in response to application of 50 mM K+. Responders were small-to-medium in size (median 25–29 μm), and cells that did not exhibit a K+-evoked GCaMP3 signal (non-responders) were ≥30 μm in size (median 45–49 μm). Data are presented in 5 μm bins. N=5.