The Effect of Trifluoperazine on Muscle Tension and Cytoplasmic Ca²⁺ Level in Guinea Pig Ileum

Abstract

In guinea pig ileal muscle strips, trifluoperazine (TFP) inhibited the high K⁺-induced contraction with an IC50 of 1.9 μM and the Ca²⁺-induced contraction in skinned fiber with an IC50 of 44 μM. TFP decreased the high K⁺-induced increase in cytoplasmic Ca²⁺ level at the concentration 3 μM, which did not inhibit the contraction in skinned fiber. It is suggested that the inhibitory effect of TFP on the high K⁺-induced contraction is mainly due to the decrease in cytoplasmic Ca²⁺.