Effects of cobalt and manganese on the calcium-action potentials in larval insect muscle fibres ( Ephestia kühniella)

Abstract

The effects of cobalt and manganese ions on the calcium action potentials in larval insect muscle fibres were investigated. 1. 1. In either cobalt or manganese (5–25 mM) containing solutions, action potentials could still be elicited by direct stimulation. The maximal rates of rise and fall of these action potentials were however considerably reduced. 2. 2. The repolarization phase of the action potentials was delayed by cobalt and manganese. 3. 3. The membrane input resistance increased in the presence of cobalt and manganese (25 mM) by a factor of 2–4, while the membrane rectification was abolished 4. 4. It is suggested that cobalt and manganese ions reduced both the inward and the outward current of the muscle membrane. These effects of cobalt and manganese are compared with those described for other excitable cells.