Dual Effects of Cyclopiazonic Acid on Excitation of Circular Smooth Muscle Isolated from the Guinea-pig Gastric Antrum

概要

論文の詳細を見る
The effects of cyclopiazonic acid (CPA), a known Ca^<2+>-pump inhibitor at internal stores, were investigated on electrical responses of the membrane of smooth muscle cells in small segments (0.3-0.5 mm long) of circular smooth muscle isolated from the guineapig gastric antrum. In most preparations, the membrane was spontaneously active with the generation of unitary potentials and regenerative slow potentials. Low concentrations (< 1μM) of CPA did not alter either the membrane potential or the amplitude and frequency of slow potentials. CPA at a concentration of 1 μM initially increased the frequency of slow potentials, but this was followed by a decrease in the frequency as a result of sustained exposure to CPA, with no alteration of either the membrane potential or the amplitude of slow potentials. Higher concentrations of CPA (2-5 μM) depolarized the membrane and decreased the amplitude and frequency of slow potentials. CPA at higher than 10 μM abolished slow potentials with depolarization of the membrane. Intracellular electrical responses recorded simultaneously from paired cells were synchronized, indicating electrical coupling of the cells. Depolarization of the membrane with current stimuli through one electrode evoked regenerative slow potentials superimposed on the electrotonic potentials. The evoked slow potential had a refractory period of about 7 s. CPA (up to 10 μM) did not prevent the synchronization of paired cells. The refractory period for slow potentials was reduced by low concentrations of CPA (< 1 μM) and increased by higher concentrations of CPA (2-10 μM). These results suggest that lower concentrations of CPA produce excitatory actions on gastric smooth muscles due to a secondary effect of increased intracellular [Ca^<2+>], while higher concentrations of CPA produce inhibitory actions as a result of reduced release of Ca^<2+> from depleted internal stores.
日本平滑筋学会の論文

Dual Effects of Cyclopiazonic Acid on Excitation of Circular Smooth Muscle Isolated from the Guinea-pig Gastric Antrum

スポンサーリンク

概要

著者

関連論文

スポンサーリンク