Effect of hyperbaric factor on lidocaine-induced apoptosis in spinal neurons in rats with diabetic neuropathic pain

Objective To evaluate the effect of hyperbaric factor on lidocaine-induced apoptosis in spinal neurons in rats with diabetic neuropathic pain.Methods Healthy male Sprague-Dawley rats,weighing 220-300 g,were used in the study.Diabetic neuropathic pain was induced by high-sugar high-fat diet + intraperitoneal 1％ streptozotocin (STZ) 30 mg/kg and confirmed by blood glucose level ＞ 16.65 mmol/L at 3 days after STZ injection and then intrathecal catheter was placed.Twenty-four rats with diabetic neuropathic pain in which IT catheters were successfully implanted were randomly divided into 3 groups (n =8 each):hyperbaric lidocaine group (group HL),isobaric lidocaine group (group IL),and glucose group (group G).Another 8 rats in which IT catheters were successfully inserted served as control group (group C).2％ hyperbaric lidocaine 10 μl (in C and HL groups),2％ isobaric lidocaine 10 μl (in group IL),or 10％ glucose 10 μl (in group G) was injected intrathecally once a day for 3 consecutive days.The duration of motor block was recorded at 2 min after each administration.The paw withdrawal threshold to von Frey filament stimulation (PWT) was measured before STZ injection (T1),before IT injection (T2),at 30 min after administration on 1st,2nd and 3rd days and on day 5 after the end of administration (T3-6).All the rats were sacrificed at T6 and their L4,5 segments of the spinal cord were removed for microscopic examination.The apoptosis in spinal neurons was detected using TUNEL assay.Results Compared with the baseline value at T1,PWT was significantly decreased at T2-5 in HL,IL and G groups.PWT was significantly higher at T6 than at T2-5 in group HL.Compared with group C,the duration of motor block was significantly prolonged and the apoptotic index was increased in group HL.Compared with group IL,the duration of motor block was significantly prolonged and the apoptotic index was increased in group HL.Conclusion Hyperbaric factor can promote lidocaine-induced apoptosis in spinal neurons in rats with diabetic neuropathic pain. Key words: Specific gravity;  Lidocaine;  Diabeties millitus;  Neuraltia;  Spinal cord;  Neurons;  Apoptosis