Fig. 2.

Optogenetic control of cellular cAMP signals reveals cell-specific responses. When bPAC was expressed in stellate cells under the control of the c724–Gal4 driver, light activation with low/intermediate intensities resulted in stimulation of fluid secretion (A,B), whereas high intensities did not affect fluid secretion (C). When expressed in principal cells under the control of c42–Gal4, bPAC stimulated fluid secretion at a light intensity of 0.2 mW/cm² (D), but higher light intensities resulted in inhibition (E,F). Genetic controls bearing one of the transgenes alone showed no change in fluid secretion when illuminated at 12.0 mW/cm² (G–I). All data are means ± s.e.m., n>20 from two independent experiments. Asterisks indicate significant differences (P<0.05).