Abstract
Cyclopiazonic acid (CPA), a novel specific inhibitor of Ca2+-ATPase in muscle sarcoplasmic reticulum, shortened the Ca2+-dependent after-hyperpolarization (AHP) following a spike in the rat superior cervical ganglion. This inhibitory effect was reversible and dependent on concentrations between 1 and 5 μM. The AHP in the presence of 5 μM CPA was not depressed further by ryanodine, nor was it affected by repetitive stimulation. These results suggest that CPA inhibits the intracellular Ca2+ release, probably due to the depletion of Ca2+ stores induced by inhibition of the ATP-dependent Ca2+ pump.
