Objective: Recently, there has been growing interest in the interaction between depressive disorders and pain. The purpose of this study was to examine whether depression would lead to a decreased sensitivity to noxious stimuli in rats with spontaneous pain.
Methods: The olfactory bulbectomized rats were used as a model of depression. The depression-like behaviors were assessed by open field test and changes in body weight. Formalin solution was injected into the rat hindpaw to produce ongoing pain. Noxious thermal stimuli were applied onto the hindpaw contralateral to formalin injection, and the withdrawal thresholds were measured.
Results: In non-depressive rats, the formalin-treated paw developed hypoalgesia to noxious stimuli while the contralateral paw was not affected. The depressive rats, however, showed a significantly lower sensitivity to noxious thermal stimulus, represented as higher withdrawal thresholds of the contralateral paw, when compared to the non-depressive rats.
Conclusion: These results demonstrate that depression can alleviate the stimulus-evoked pain even in the context of formalin inflammatory pain, consistent with the previous clinical observations that patients suffering from both depression and persistent pain have decreased sensitivities to noxious experimental stimuli.
目的: 近年来, 人们对抑郁症和疼痛之间的相互作用日益关注。 本研究通过观察抑郁对福尔马林注射大鼠的伤害性阈值的影响, 探讨抑郁能否降低伴有自发痛的大鼠对伤害性刺激的感受性。
方法: 通过嗅球切除术建立大鼠抑郁模型, 并采用旷场测试和体重变化来评价抑郁行为。 在大鼠后肢足底注射福尔马林溶液诱导持续性疼痛。 在福尔马林注射的对侧后肢足底施加伤害性辐射热刺激, 测定其抬脚阈值。
结果: 在非抑郁大鼠中, 福尔马林注射肢对伤害性刺激表现出痛觉减退, 而对侧肢的伤害性阈值则不受影响。 然而, 与非抑郁大鼠相比, 抑郁大鼠对伤害性热辐射刺激的感受性显著降低, 表现为对侧后肢抬脚潜伏期延长。
结论: 上述结果表明, 在伴有福尔马林炎症痛的条件下, 抑郁同样能降低机体对诱发痛的敏感性。 该结果与临床上关于同时患有抑郁与慢性痛患者对实验性痛刺激感受性下降的观察结果一致。