Cyclopiazonic acid disturbs the regulation of cytosolic calcium when repetitive action potentials are evoked in Dionaea traps.

Evoking of action potentials (APs) in the trap of Dionaea muscipula Ellis at intervals shorter than 20 s caused a gradual decrease in the amplitude of the APs. At longer intervals the amplitude was constant. The calcium ionophore A23187 (1 μM) caused a considerable decrease of AP amplitude. Pretreatment of a segment of the Dionaea trap with cyclopiazonic acid (CPA), which is a specific inhibitor of the Ca-ATPase in the sarcoplasmic seticulum of animal cells and in ER vesicles isolated from plant cells, only slightly affected the amplitude when APs were evoked every 10 min; however, it caused a considerable decrease in the amplitude when the stimulation was repeated every 2 min. Assuming that APs increase the concentration of cytosolic Ca and the amplitude of AP depends on the gradient of Ca across the plasma membrane, the effect of CPA on the AP amplitude indicates that CPA inhibits the sequestration of Ca in Dionaea cells.