Abstract

Calcium channels modulate cell function by controlling Ca²⁺influx. A main component of these proteins is the α2/δ subunit. Nevertheless, how this subunit regulates channel activity in situ is unclear. Gabapentin (GBP), an analgesic and anti-epileptic agent with an unknown mechanism of action, specifically binds to the α2/δ subunit. Using the patch clamp technique, we tested the effects of GBP on Ca²⁺ currents from dorsal root ganglion (DRG) cells, the mediators of pain perception, to determine how GBP binding modifies channel activity. In DRGs, GBP significantly reduced whole cell Ca²⁺ current amplitude at positive membrane potentials when a pulse preceded the test pulses or when cells were stimulated with a train of pulses. In control cells, neither prepulse depolarization nor pulse trains reduced Ca²⁺ currents at positive potentials. GBP did not reduce the low-voltage activated Ca²⁺ current under any experimental condition. Similar to DRG cells, GBP attenuated Ca²⁺ current in skeletal myotubes at positive membrane potentials in the presence of a depolarizing prepulse. However, GBP did not significantly alter Ca²⁺ currents in cardiac myocytes. Reverse transcription-polymerase chain reaction was used to confirm expression of the α2/δ subunit in these cells. Each cell type expressed multiple isoforms of α2/δ. Muscle cells showed a more variable expression of α2/δ subunits than did DRG cells. Our results suggest a possible participation of the α2/δ subunit in the action of GBP. Our data also indicate that GBP inhibits Ca²⁺ channels in a use- and voltage-dependent manner at a therapeutically relevant concentration.