Fig. 4

Monitoring of activity-driven Ca²⁺ dynamics in CStr circuits in the electrostimulable microfluidic device using Physin-GC6f. A Representative Physin-GC6f images of Ca²⁺ dynamics in response to neural activity (10 AP stimulus) at synapses of CStr circuits. Left, resting; middle, ∆F10AP; right, peak 10 AP. Scale bar: 20 μm. B Kymograph images of Physin-GC6f showing Ca²⁺ dynamics at the corresponding ROI in boutons in the synapse canal of the microfluidic chip in response to stimulation with 10 APs. Arrow indicates point of stimulation. C Representative ensemble Physin-GC6f traces showing Ca²⁺ dynamics in response to microfluidic chip stimulation with 10 APs or 1 AP. D Ca²⁺ influx, in arbitrary units (a.u.), in response to microfluidic chip stimulation with 10 APs or 1 AP, expressed as means ± SEM. [Ca²⁺]_10AP = 7.17 ± 0.82 a.u. (n = 10); [Ca²⁺]_1AP = 0.54 ± 0.10 a.u. (n = 10). E, F Distribution of Ca²⁺-influx responses to 10 APs (E; n = 305) and 1 AP (F; n = 324) in individual boutons. G Representative traces of Ca²⁺ dynamics in response to paired-pulse stimulation at different pulse intervals (100, 200 and 500 ms). Arrows indicate the point of stimulation