Fig. 8.

S1P generates La³⁺-sensitive Ca²⁺ elevations in amacrine cells. Cells were loaded for 1 h with the Ca²⁺- sensitive dye Oregon Green BAPTA 488. A: a representative example of a fluorescence recording testing the effects of the vehicle for S1P (1% Met-OH) and N,N-dimethyl-d-erythro-sphingosine (DMS, 1% Et-OH), a reagent used in the experiments depicted in Fig. 11. No Ca²⁺ elevations were seen in response to these compounds. B: a representative recording shows that 1 μM S1P can elicit La³⁺-sensitive Ca²⁺ elevations. C: data from a different cell showing a La³⁺-sensitive cytosolic Ca²⁺ increase to 10 μM S1P. Inset: data from a different cell showing that in the absence of La³⁺, the Ca²⁺ elevations can persist well after the removal of S1P (scale bars are 1.1 F/F₀ and 30 s). D: in 0-Ca²⁺, a small S1P-dependent Ca²⁺ increase was observed, likely representing release of Ca²⁺ from internal stores. Re-introduction of external Ca²⁺ produced a dramatic increase in the S1P-dependent Ca²⁺ elevation. E: an amacrine cell preloaded with Oregon Green Bapta 488 is voltage-clamped at −70 mV in the perforated-patch configuration. S1P causes a cytosolic Ca²⁺ increase that precedes the inward S1P-dependent current. F: in a different cell, S1P-induces a cytosolic Ca²⁺ increase that occurs simultaneously with the S1P-dependent current.