Sphingolipid derivatives modulate intracellular Ca2+ in rat synaptosomes.

Sphingosylphosphorylcholine (SPC) induces a rapid increase of intracellular Ca2+ concentration in isolated synaptosomes. This effect is dose-dependent and is also dependent on extracellular Ca2+. 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 Ca2+ release agonist in synaptosomes. Experiments performed in the presence of heparin or ryanodine indicate that SPC-elicited Ca2+ release is not mediated by IP3 or ryanodine receptors. Finally, our results show that the effect of SPC on Ca2+ concentration is nimodipine-sensitive, suggesting that SPC possibly activates a specific sphingolipid-gated Ca2+ channel in synaptosomes.