Cilioinhibitory effect of phenothiazines in vitro and its antagonism by Ca++.

The inhibition of ciliary beating in vitro by physiologic concentrations of chlorpromazine (CPZ) and prochlorperazine (PCP) was demonstrated in two experimental systems. CPZ had a greater cilioinhibitory effect than PCP on the rotational velocity of tissue explants from the frog palate in amphibian Ringers, and on the frequency of ciliary beating in rat tracheal rings in culture medium. Addition of calcium acetate in equal molarity to CPZ, within a time limit dependent on the drug concentration, reversed this inhibition, while dibutyryl cyclic AMP did not. Simultaneous addition of Ca++ and CPZ slowed down, but did not stop, this ciliostasis, while priming with Ca++ or cyclic AMP prior to drug addition had less of an effect. These data lend support to a prevalent theory that CPZ exerts its actions by displacing calcium ions from membrane sites.