Haloperidol modulates ion transport in <Emphasis Type="Italic">Chara corallina</Emphasis> cells

The effects of haloperidol, an antagonist of D2 dopamine receptors, on the functioning of Ca²⁺, K⁺, and Cl^? ion channels in the membrane of Chara corallina cells and on the functional properties of their cytoskeleton was studied. Haloperidol blocked Ca²⁺ channels of the plasmalemma. In addition to bringing about a decrease in the amplitude of the calcium current, exposure to haloperidol decelerated the activation and inactivation of calcium channels. The effect of haloperidol was reversible; after it was removed, the characteristics of calcium current were restored. Haloperidol did not affect Ca²⁺-activated chloride channels. Haloperidol also inhibited microfilament-dependent motion of the cytoplasm. Cytoplasmic streaming was restored after haloperidol was removed from the extracellular solution. These results suggest that the concentration of free Ca²⁺ ions in the cytoplasm increases in the presence of haloperidol, and that Ca²⁺ channels of C. corallina plasmalemma possess specific binding sites both for dopamine receptors and for their antagonists.