Peritoneal macrophages were isolated from wild type (WT) mice and from mice invalidated for the P2X7 receptor (KO) which had been pretreated with thioglycolate. In cells from WT mice, 1 mM ATP increased the intracellular concentration of calcium ([Ca2+] i), the uptake of ethidium bromide, the production of reactive oxygen species (ROS), the secretion of IL-1β, the release of oleic acid and of lactate dehydrogenase; it decreased the intracellular concentration of potassium ([K+] i). In KO mice, ATP transiently increased the [Ca2+] i confirming that the P2X7 receptor is a major receptor of peritoneal macrophages. WKYMVm, an agonist of receptors for formylated peptides (FPR) also increased the [Ca2+] i in murine macrophages. The slight increase of the [Ca2+] i was strongly potentiated by ivermectin confirming the expression of functional P2X4 receptors by murine peritoneal …