Effects of carbamazepine on membrane properties of rat sensory spinal ganglion cells in vitro.

The present study aimed to examine effects of the antiepileptic drug carbamazepine (CBZ) on membrane properties. Therefore, effects of CBZ on voltage-dependent ion channels were investigated in rat sensory spinal ganglion cells in primary cultures. (i) Membrane potentials and action potentials were recorded by sharp microelectrodes: CBZ reduced neuronal excitability without changing the resting membrane potential, and suppressed tetrodotoxin (TTX)-resistant components of action potentials which were blocked by cobalt and hence were interpreted as Ca2+ spikes. The rising phase and peak amplitude of TTX-sensitive components of action potentials, however, were hardly altered. (ii) Voltage-dependent inward and outward currents were elicited in the whole-cell configuration of the patch clamp technique. CBZ reduced (presumably L-type) Ca2+ currents. In some cells Ca2+ currents partly recovered during washing with control saline. The effects on Na+ and K+ currents were not uniform and often insignificant. The present study indicates that CBZ has calcium-antagonistic properties.