Acetylcholine-induced Ca2+ signaling in mouse peritoneal macrophages

To investigate modulatory effects of the parasympathetic nervous system on the immune system, effect of acetylcholine (ACh) on mouse peritoneal macrophages were examined by measuring an intracellular Ca2+ concentration ([Ca2+](i)) ACh stimulated an increase in [Ca2+](i) in the macrophages. In the presence of atropine, a competitive antagonist for muscarinic acetylcholine receptors, the increase was suppressed. Furthermore, the ACh-induced increase in [Ca2+](i) was not inhibited in a Ca2+-free/EGTA containing external solution. The results indicate that ACh activates release of Ca2+ from internal stores through an activation of muscarinic receptors and suggest that the immunological responses mediated by macrophages can be modulated by activities of the cholinergic nerves.