Sphingosine at the concentration of 100 muM is depleting ER calcium stores, causing a rise in intracellular calcium ranging from 50 to 100 nM. It also decreases Ca2+ response caused by 100 nM thapsigargin. Preincubation with 10 mM neomycin, a high affinity ligand for PIP2, which inhibits PLC and PLD activitity in brain, partially eliminates the effect of sphingosine on thapsigargin elicited Ca2+ signal. This effect is not observed after preincubation with 150 mM ethanol, which acts as a substrate for PLD, blocking its normal activity by production of phosphatidylethanol instead phosphatidic acid. These results suggest that sphingosine may act on intracellular Ca2+ stores and stimulate Ca2+ mobilization via process mediated rather by PLC than by PLD activation.ion.