Figure 6.

Differential TRPV4 channel activation mediates neuronal and glial responses to swelling. A, Changes in the volume of calcein-loaded Müller cells were apparent when switching from isotonic (Ai) to hypotonic saline (Aii). Aiii, The volume changes were approximated by measuring cell area. Black represents isotonicity; gray represents hypotonicity. Scale bar, 10 μm. B, Müller glia and RGCs swelled and shrunk as a function of tonicity. C, HTS elevated Müller cell calcium as they swelled in a representative experiment. D, Swelling-evoked calcium elevations were dose-dependent (95% confidence band around the sigmoidal fit). n = 13–20. E, Swelling-evoked [Ca²⁺]_MC elevations required external calcium. F, PLA2 and TRPV4 contribute substantially to the hypoosmotic response of Müller glia. n = 10, 13, and 11, respectively. G, The PLA2 antagonist pBPB has no effect on RGC responses to cell swelling, even though these responses are mediated largely by TRPV4. n = 23, 16, and 9, respectively. H, I, The 50% HTS evoked inward currents in Müller glia (n = 7) that were absent in the presence of HC-06 (n = 8) or in TRPV4^−/− cells (n = 7). J, Müller glia responsiveness to 35% HTS (n = 10 experiments) is reduced by the TRP channel antagonist Ruthenium Red (RuR 10 μm; n = 5) or 1 μm HC-06 (n = 6), but not the TRPV1 antagonist capsazepine (CPZ 10 μm; n = 3). K, RGC responsiveness to HTS (n = 6) is impaired by Ruthenium Red (n = 6) and HC-06 (n = 6), but not TRPV1 inhibition (n = 3). NS, Not significant (p > 0.05). *p < 0.05. **p < 0.01. ***p < 0.001.