Fig. 5

GtACR1 activation depolarizes ventricular myocyte membrane potential in isolated zebrafish hearts. Regions of high or no eGFP expression on the ventricle of 3-months post fertilization (mpf) zebrafish isolated hearts were illuminated by a 0.16 mm² spot of 531/22 nm light sustained for 15 s or pulsed for 10 ms at a rate 2–3 × sinus heart rate. (A,D–E) In the case of sustained light, in regions displaying eGFP expression (red circle in C) there was an immediate increase in resting membrane potential (E_R) and a decrease in the maximum rate of membrane depolarization (dE/dt_max), AP amplitude (AP_Amp), and APD at 50% and 90% repolarization (APD₅₀ and APD₉₀). (B) In the case of pulsed light, the heart could be stimulated when light intensity was increased to supra-threshold values. (A,B) In both cases, there was no effect seen in regions displaying no eGFP expression (blue circle in C). *indicates p < 0.0001 by two-tailed paired Student's t-test.