(A) Ex vivo choroid plexus was incubated in Fluo-4 calcium indicator dye to study calcium influx into the epithelial cells. Ionomycin (100 μM) was used as a positive control for calcium influx, and GSK1016790A (3 nM) was used to agonize TRPV4. TRPV4 activation generated a qualitative increase in fluorescent signal, consistent with allowing calcium influx into the cells. (B) Ex vivo choroid plexus was incubated in CoroNa Green Sodium indicator dye to study sodium influx into the epithelial cells. Nystatin (100 μM) was used as a positive control for sodium influx, and GSK1016790A (3 nM) was used to agonize TRPV4. TRPV4 activation generated a qualitative increase in fluorescent signal, consistent with allowing sodium influx into the cells. TRPV4, transient receptor potential vanilloid 4; GSK, GSK1016790A. Original magnification, 40×.