LYSOSPHINGOMYELIN-ELICITED CA2-BRAIN MICROSOMES( MOBILIZATION FROM RAT)

We have examined the Ca2+ release activity of sphingolipid-derivatives from rat brain microsomes using a Fura-2 cytofluorometric assay. Sphi ngosylphosphorylcholine, lysosphingomyelin, elicited a rapid Ca2+ rele ase from both cerebral and cerebellar microsomes. Other compounds incl uding sphingosine and sphingosine-1-phosphate were incapable of causin g the Ca2+. release. The pharmacological properties suggest that the s phingosylphosphorylcholine-elicited Ca2+ mobilization is not mediated by inositol 1,4,5-triphosphate receptors. Immunocytochemical study sho w ed the occurrence of sphingomyelin, a putative precursor for sphingo sylphosphorylcholine, in the somatodendritic membrane domains of cereb ellar neurons. These observations imply that sphingosylphosphorylcholi ne is a potent Ca2+ releaser in brain neurons.