| Abstract: | Calmodulin (CaM) regulation of cholinergic muscarinic receptor was investigated using synaptic membrane isolated from rat brains and 3H]-QNB as a binding ligand. CaM exerts a biphasic effect on receptor binding showing both a Ca2+-dependent receptor loss and an increase depending on the state of membrane phosphorylation. Calcineurin, a CaM-dependent protein phosphatase, mimicked the stimulatory effect of CaM in a dose-dependent manner. CaM-antagonists, W-7 and TFP reversed the stimulatory effect by CaM. A mechanism of protein phosphorylation and dephosphorylation of the cholinergic muscarinic receptors regulated by CaM-Ca2+ was proposed. |
