Gabapentin is used as an effective drug for relieving pain, but the main mechanism is still unclear. Recently, voltage-gated Ca2+ channel subunits are suggested for the main target for the analgesic action of gabapentin. We wonder whether gabapentin directly modulates other specific ion channels peripherally expressed in the sensory neurons. To test this, we used a heterologous expression system in which the cell lines transiently expressed thermosensitive transient receptor potential ion channels (thermoTRPs) as well as the primary cultured mouse trigeminal neurons. The application of gabapentin reduced the increases in the intracellular Ca2+ level caused by TRPA1 activation in the heterologous expression system whereas the responses via actions of other thermoTRPs were not dramatically affected by the gabapentin treatment. Gabapentin also attenuated the TRPA1-mediated intracellular Ca2+ increases in the cultured trigeminal neurons. These findings suggest TRPA1 in the peripheral sensory neurons as a novel target for the analgesic of gabapentin.
Acrolein ; Amines ; Animals ; Cell Line ; Cyclohexanecarboxylic Acids ; gamma-Aminobutyric Acid ; Ion Channels ; Mice ; Neurons ; Sensory Receptor Cells ; Trigeminal Ganglion

The voltage-gated Na channel subtype Nav1.7 is important for pain and itch in rodents and humans. We previously showed that a Nav1.7-targeting monoclonal antibody (SVmab) reduces Na currents and pain and itch responses in mice. Here, we investigated whether recombinant SVmab (rSVmab) binds to and blocks Nav1.7 similar to SVmab. ELISA tests revealed that SVmab was capable of binding to Nav1.7-expressing HEK293 cells, mouse DRG neurons, human nerve tissue, and the voltage-sensor domain II of Nav1.7. In contrast, rSVmab showed no or weak binding to Nav1.7 in these tests. Patch-clamp recordings showed that SVmab, but not rSVmab, markedly inhibited Na currents in Nav1.7-expressing HEK293 cells. Notably, electrical field stimulation increased the blocking activity of SVmab and rSVmab in Nav1.7-expressing HEK293 cells. SVmab was more effective than rSVmab in inhibiting paclitaxel-induced mechanical allodynia. SVmab also bound to human DRG neurons and inhibited their Na currents. Finally, potential reasons for the differential efficacy of SVmab and rSVmab and future directions are discussed.
Animals ; Antibodies, Monoclonal ; therapeutic use ; Biotin ; metabolism ; Cells, Cultured ; Disease Models, Animal ; Female ; Ganglia, Spinal ; cytology ; HEK293 Cells ; Humans ; Hybridomas ; chemistry ; Hyperalgesia ; drug therapy ; Male ; Mice ; Mice, Inbred C57BL ; NAV1.5 Voltage-Gated Sodium Channel ; metabolism ; NAV1.7 Voltage-Gated Sodium Channel ; chemistry ; immunology ; metabolism ; Neuralgia ; drug therapy ; metabolism ; Protein Binding ; drug effects ; Recombinant Proteins ; biosynthesis ; therapeutic use ; Sensory Receptor Cells ; drug effects ; physiology