Myoepithelial cells were isolated from the apical ends of mesenteries of the sea anemone Calliactis tricolor and examined using the whole-cell configuration of the patch-clamp technique. The isolation procedure produced cell fragments that were contractile and produced action potentials when depolarized. These action potentials are formed by a complex array of ionic currents consisting of at least one, and possibly two, inward calcium currents and four outward potassium currents. The ionic selectivity of the calcium currents was Ca2+>Sr2+>Ba2+. Outward currents consisted of a calcium-dependent outward current and three voltage-activated currents, including a 4-aminopyridine-sensitive current, a transient outward current and a steady-state current.

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