The plasma membrane of cells from rat submandibular glands was isolated and extensively sonicated. The homogenate was centrifuged at high speed in a discontinuous sucrose gradient. Light fractions contained vesicles analogous to rafts: they were rich in cholesterol, they contained GM1 and caveolin-1, and P2X 7 receptors were detected in these fractions. The location of the P2X 7 receptors in rafts was abolished when cellular cholesterol was removed by methyl-β-cyclodextrin (MCD). ATP activated neutral sphingomyelinase (N-SMase), which provoked a decrease of the cellular content of sphingomyelin and an increase of ceramide levels in these cells and in the rafts. Treatment with MCD and filipin (but not with α-cyclodextrin) abolished the increase of the intracellular concentration of calcium ([Ca 2+] i) in response to epinephrine but not to ATP. MCD and filipin also …