Analgesic effect of intrathecal recombinant adenovirus containing human beta-endophin gene in a rat model of neuropathic pain / 中华麻醉学杂志

ABSTRACT

Objective To examine the analgesic effect of intrathecal (i.t.) adenovirus containing human beta-endorphin (?-EP) gene in a rat model of neuropathic pain produced by chronic constrictive injury (CCI) . Methods Thirty-six male SD rats weighing 210-260 g were randomly divided into 3 groups: (1) blank control group (n = 5); (2) sham-operated group (n = 5) ; (3) neuropathic pain group (n = 26) . The neuropathic pain group was further divided into 3 subgroups: Ad-NEP subgrouop (n = 9); Ad-GFP (the recombinant adenovirus containing green fluorescent protein) subgroup (n = 9) and normal saline (NS) subgroup (n = 8). The animals were anesthetized with intraperitoneal ketamine 100 mg?kg-1 and atropine 50 mg?kg-1. Neuropathic pain was produced by ligation of right sciatic nerve according to the technique described by Bennet and Xie. In sham-operated group the sciatic nerve was exposed but not ligated. In blank control group no operation was performed. Seven days after the surgery a PE-10 catheter was placed in the subarachnoid space at L5,6 according to the method of Milligan et al. Seven days after catheter placement 1?108 pfu Ad-NEP, Ad-GFP and 0.9% saline were injected i.t. via the catheter respectively. The paw-withdrawal latency to radiant heat was measured before surgery (T0,baseline) , the day of i.t. injection (T1) and 1 day (T2) , 1 w (T3), 2 w (T4), 3 w (T5), 4 w (T6) 5 w (T7) after i.t. injection. At one week after i.t. administration one animal in Ad-NEP subgroup and Ad-GFP subgroup was killed and the lumbar segment (L3-6) of the spinal cord was removed for immuno-histochemical examination. Naloxone 1 mg?kg-1 was given intraperitoneally in Ad-NEP subgroup (n = 8) and Ad-GFP subgroup (n = 8) at 10 days after i.t. injection. Pain threshold to thermal stimulation of the right paw was measured before (t0) and from 10-90 min after intraperitoneal naloxone injection at an interval of 10 min (t1-9). CSF samples were obtained at T1-7 for determination of CSF concentration of ?-EP using radio-immunological assay. Results The right paw-withdrawal latencies (PWLs) were significantly lower in Ad-GFP subgroup and NS subgroup than in blank control and sham-operated groups (P