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Divalent cations and the action potential of leech Retzius cells
Pflugers Archiv : European Journal of Physiology
|May 12, 1976
Summary
Strontium and barium ions can carry current in leech Retzius cells, while manganese and lanthanum block calcium-dependent action potentials. Divalent cations likely use the same channels as sodium ions.
Area of Science:
- Neuroscience
- Cell Physiology
- Ion Channel Pharmacology
Background:
- Leech Retzius cells exhibit calcium-dependent action potentials in sodium-free solutions when outward potassium current is blocked.
- Previous research established the conditions for calcium-dependent firing in these cells.
Purpose of the Study:
- To investigate the effects of strontium (Sr), barium (Ba), manganese (Mn), lanthanum (La), and cobalt (Co) on leech Retzius cell action potentials.
- To characterize the ion channels involved in action potential generation in these cells.
Main Methods:
- Intracellular recording techniques were employed to study the electrical activity of Retzius cells.
- Experiments were conducted in both normal Ringer solutions and sodium-free solutions with specific ion substitutions and blockers.
Main Results:
- Strontium (Sr) substituted for calcium (Ca) as a current carrier in sodium-free solutions.
- Barium (Ba) prolonged and increased the amplitude of action potentials, supporting firing without tetraethylammonium (TEA).
- Manganese (Mn) and lanthanum (La) selectively blocked the inward divalent cation current component of the action potential, sparing sodium-dependent depolarization.
Conclusions:
- Outward potassium current blockade is necessary for divalent cations to influence Retzius cell excitation.
- The divalent cation channel is pharmacologically distinct from the sodium channel but similar to channels in other excitable membranes.
- Current-carrying divalent cations likely utilize the same channel.