加巴喷丁对慢性疼痛和抑郁共病成年大鼠海马齿状回神经发生的影响

Effect of gabapentin on neurogenesis in hippocampal dentate gyrus of adult rats with co-disease of chronic pain and depression

目的:持续3个月以上的慢性疼痛往往合并抑郁、焦虑等负性情绪。长期的慢性疼痛应激可以导致海马结构和功能上的可塑性改变。加巴喷丁除镇痛作用外,同时具有一定的脑保护作用。本研究观察加巴喷丁对慢性疼痛和抑郁共病成年大鼠海马齿状回(dentate gyrus,DG)神经发生的影响。方法:将成年Sprague-Dawley(SD)大鼠随机分成4组:假手术(Sham)组、共病模型+生理盐水(CCI+Veh)组(1 m L生理盐水)、共病模型+低剂量加巴喷丁(CCI+LG)组(将加巴喷丁用生理盐水稀释至1 mL,加巴喷丁剂量为30 mg/kg)、共病模型+高剂量加巴喷丁(CCI+HG)组(将加巴喷丁用生理盐水稀释至1 mL,加巴喷丁剂量为100 mg/kg),每组8只。采用坐骨神经环扎造成慢性压迫性损伤(chronic constrictive injury,CCI)建立共病模型。于手术后第30天开始经腹腔注射给药,连续7 d。测定大鼠术前1天及术后第7、14、21、28、40天右后肢的机械缩足反射阈值(paw withdrawal mechanical threshold,PWMT);术后第28、40天进行强迫游泳实验及糖水偏爱实验并测量被动漂浮时间和糖水偏爱率;采用免疫组织化学染色观察海马DG的神经元双皮质素(doublecortin,DCX)阳性神经元数目和脑源性神经营养因子(brain-derived neurotrophic factor,BDNF)表达,高尔基染色观察大鼠海马神经元结构。结果:与Sham组相比,CCI共病模型大鼠PWMT术后第7天达到最低值并持续至术后第28天,第40天仍处于较低水平(均P<0.05);与CCI+Veh组相比,术后第40天CCI+LG组、CCI+HG组大鼠PWMT均有提高(均P<0.05)。与Sham组相比,CCI共病模型大鼠在术后第28天被动漂浮时间显著增长(均P<0.01),糖水偏爱率显著降低(均P<0.01);与CCI+Veh组相比,CCI+HG组大鼠在术后第40天被动漂浮时间缩短(P<0.05),糖水偏爱率显著增加(P<0.01)。与CCI+Veh组相比,CCI+LG组和CCI+HG组的大鼠海马DG的DCX阳性细胞增加,且CCI+HG组增加更加明显(P<0.05);与Sham组相比,CCI+Veh组大鼠的海马DG的BDNF表达水平下降(P<0.05);与CCI+Veh组相比,CCI+HG组大鼠的海马DG的BDNF表达水平上升(P<0.05),海马神经元树突棘的长度增加(P<0.05)。结论:加巴喷丁可缓解慢性疼痛和抑郁共病模型大鼠慢性疼痛及抑郁样行为,促进其海马齿状回神经元的神经发生。

Objective:Chronic pain lasts for more than 3 months and is often associated with negative emotions such as depression and anxiety.Long-term chronic pain stress can lead to plastic changes in hippocampal structure and function.In addition to its analgesic effect,gabapentin also has certain cerebral protective effects.This study aims to observe the effect of gabapentin on neurogenesis in hippocampal dentate gyrus(DG)of the adult rats with codisease of chronic pain and depression.Methods:The adult rats were randomly divided into 4 groups:A sham operation(Sham)group,a comorbidity model+normal saline(CCI+Veh)group(1 m L saline),a comorbidity model+low-dose gabapentin(CCI+LG)group(diluting gabapentin with normal saline to1 mL at the dose of 30 mg/kg),and a comorbidity model+high-dose gabapentin(CCI+HG)group(diluting gabapentin with normal saline to 1 mL at the dose of 100 mg/kg)(8 rats per group).The comorbidity model was established by sciatic nerve encirclement.On the 30th day after operation,normal saline,low-dose gabapentin,and high-dose gabapentin were given intraperitoneally,respetively,for 7 consecutive days.The paw withdrawal mechanical threshold(PWMT)of the right hindlimb was measured before the operation and on the 7th,14th,21th,28th,and 40th day after the operation.The time of immobility and sugar water preference rate were measured by forced swimming test and sugar water preference test,respectively,on the 28th and 40th day after the operation.The number of doublecortin(DCX)positive neurons and the expression of brain-derived neurotrophic factor(BDNF)in hippocampal dentate gyrus were observed by immunohistochemical staining,and the morphological changes of the hippocampal neurons were observed by Golgi staining.Results:Compared with the Sham group,the PWMT of the CCI comorbidity model rats reached the lowest level on the 7th day after the operation and lasted until the 28th day after the operation,and remained at a low level on the 40th day after the operation(all P<0.05).Compared with the CCI+Veh group,the PWMT in the CCI+LG group and the CCI+HG group was increased on the 40th day after the operation(all P<0.05).Compared with the Sham group,the time of immobility in the CCI comorbidity model rats was increased significantly(all P<0.01)and the sugar water preference rate was decreased significantly(all P<0.01)on the 28th day after the operation.Compared with the CCI+Veh group,the time of immobility in the CCI+HG group was shortened(P<0.05)and the sugar water preference rate was significantly increased(P<0.01)on the 40th day after the operation.Compared with the CCI+Veh group,the number of DCX positive cells in hippocampal DG of the CCI+LG group and the CCI+HG group was increased,and that in the CCI+HG group was increased more significantly(P<0.05).Compared with the Sham group,the expression of BDNF in hippocampal DG was decreased in the CCI+Veh group(P<0.05).Compared with the CCI+Veh group,the expression of BDNF in hippocampal DG and the length of dendritic spines of the hippocampal neurons were increased in the CCI+HG group(all P<0.05).Conclusion:Gabapentin can relieve chronic pain and depression-like behavior in rats with chronic pain and depression,and promote neurogenesis of hippocampal dentate gyrus neurons.