Representative traces illustrating the effect of cer, sph, and SPP on 340:380 fluorescence intensity ratio in fura-2-loaded neonatal OLGs. An increase in 340:380 ratio indicates an increase in Ca_i. A, cer (1–10 μm). B, sph (30 μm), followed by washout with NB and Ca²⁺-free solutions.C, SPP (5 μm). Note that 0.1% BSA and 0.1% DMSO had no effect on OLG Ca_i. D, cer, SPP, and sph in Ca²⁺-free solution (1 EGTA, 0 Ca²⁺).