Effects of gabapentin on high-voltage-activated calcium currents in dorsal root ganglion neurons in mice with oxaliplatin-induced neuropathic pain

Objective To investigate the effects of gabapentin on high-voltage-activated calcium currents in dorsal root ganglion (DRG) neurons in mice with oxaliplatin-induced neuropathic pain (NP). Methods Pathogen-free male Kunming mice aged 6 weeks weighing 20-25 g were used in this study. NP was induced by injection of intraperitoneal oxaliplatin 3 mg/kg. Successful induction of NP was defined as the mechanical paw withdrawal threshold (MWT) measured at 3 d after oxaliplatin administration decreased to 40% of the baseline ( before administration of oxaliplatin). Forty-one mice in which NP was successfully induced were randomly divided into 2 groups: NP group ( n = 20) and gabapentin group (group G, n = 21 ). Another 10 normal mice served as control group (group C). At 3 days after oxaliplatin administration, gabapentin 100 mg/kg was injected intraperitoneally once a day for 3 consecutive days in group G, while C and NP groups received the equal volume of normal saline.MWT to von Fray filament stimulation was measured immediately before and 1-3 days after gabapentin administration (T1-4). After the last measurement of MWT, bilateral L4.5 DRG was collected and neurons were isolated. The high-voltage-activated calcium currents were recorded using whole-cell patch-clamp technique. The peak current density and the voltage where half of the current was activated ( Va1/2 ) or inactivated ( Vi 1/2 ) were calculated. Results Compared with group C, MWT at T1-4 was decreased, the peak current density and Vi1/2 were significantly increased in group NP, and MWT at T1 was decreased in group G ( P ＜ 0.05). There was no significant difference in the peak current density, Vi1/2 and Va1/2 between C and G groups ( P ＞ 0.05). MWT at T2-4 was significantly increased, while the peak current density and Vi1/2 were significantly decreased in group G compared with group NP (P ＜ 0.05). Conclusion Gabapentin can reduce oxaliplatin-induced NP in mice through inhibiting high-voltage-activated calcium currents and promoting the inactivation of the channels in DRG neurons. Key words: Cyclohexanecarboxylic acids;  Antineoplastic combined chemotherapy protocols;  Neuralgia;  Calcium channels;  Ganglia, spinal