FIGURE 2.

A specific subpopulation of astrocytes responds to a chemical TRPV4 agonist and initiates Ca²⁺ oscillations. A, representative pictures of Ca²⁺ imaging experiments (see supplemental Movie 1). Cultured astrocytes were exposed to 4αPDD. Ca²⁺ influx was observed only in TRPV4⁺ populations (at 50 s). After the observed increase in [Ca²⁺]_i exclusively in TRPV4⁺ astrocytes, significant Ca²⁺ oscillations were observed in most of the other astrocytes (at 620–720 s). B, representative traces from cells exposed to 4αPDD (10 μm) are shown in the upper graph. The pink trace is from a TRPV4⁺ cell. Representative traces from cells exposed to both 4αPDD (10 μm) and octanol (3 mm) are shown in the lower graph. The pink trace is from a TRPV4⁺ cell. Arrowheads indicate Ca²⁺ spikes in TRPV4⁻ cells. C, quantification of 4αPDD-evoked activation of TRPV4 compared with the response in WT astrocytes. D, quantification of the number of Ca²⁺ spikes evoked by exposure to 4αPDD compared with the number evoked in WT astrocytes. *, p < 0.01, t test (versus WT).