Sphingolipid derivatives modulate intracellular Ca2+ in rat synaptosomes

Sphingosylphosphorylcholine (SPC) induces a rapid increase of intracellular Ca 2+ concentration in isolated synaptosomes. This effect is dose-dependent and is also dependent on extracellular Ca 2+ . Sphingosine (SPH) has a smaller effect and treatment with psychosine (PSY) is ineffective, which suggests that phosphorylation of the 1-carbon of SPH is required for the SPC to act as a Ca 2+ release agonist in synaptosomes. Experiments performed in the presence of heparin or ryanodine indicate that SPC-elicited Ca 2+ release is not mediated by IP3 or ryanodine receptors. Finally, our results show that the effect of SPC on Ca 2+ concentration is nimodipine-sensitive, suggesting that SPC possibly activates a specific sphingolipid-gated Ca 2+ channel in synaptosomes.