Calcium-dependent action potentials in mouse spinal cord neurons in cell culture

Following blockade of membrane potassium conductance with tetraethylammonium ions or 3-aminopyridine, long-duration action potentials were recorded from mouse spinal cord neurons in primary dissociated cell culture. The action potentials were calcium-dependent since they: (1) were not blocked by the sodium-channel blocker tetrodotoxin, (2) could be recorded in sodium-free, calcium-containing medium (3) could not be evoked in sodium-containing, calcium-free medium, (4) were blocked by calcium channel blockers manganese and cobalt and (5) had overshoot amplitudes that varied linearly with the log of the extracellular calcium concentration (slope of 27.5 mV/decade change in calcium concentration).