• European Marine Science
• Experimental Physiology close

Voltage‐dependent calcium currents in vertebrate (Scyliorhinus canicula), protochordate (Branchiostoma lanceolatum), and invertebrate (Alloteuthis subulata) skeletal and striated muscle were examined under whole‐cell voltage clamp. Nifedipine (10 μM) suppressed and cobalt (5 mM) blocked striated/skeletal muscle calcium currents in all of the animals examined, confirming that they are of the L‐type class. Calciseptine, a specific blocker of vertebrate cardiac muscle and neuronal L‐type calcium currents, was applied (0.2 μM) under whole‐cell voltage clamp. Protochordate and invertebrate striated muscle L‐type calcium currents were suppressed while up to 4 μM calciseptine had no effect on dogfish skeletal muscle L‐type calcium currents. Our results demonstrate the presence of at least two sub‐types of L‐type calcium current in these different animals, which may be distinguished by their calciseptine sensitivity. We conclude that the invertebrate and protochordate L‐type current sub‐type that we have examined has properties in common with vertebrate ‘cardiac’ and ‘neuronal’ current sub‐types, but not the skeletal muscle sub‐type of the L‐type channel.