中脑导水管周围灰质腹外侧区GABAAα3及GABAB受体在调节急性疼痛中的作用

Role of GABAA_(α3) and GABAB receptors in ventrolateral periaqueductal gray in rats with acute pain

目的观察大鼠足底注射甲醛复制急性疼痛模型后大鼠中脑导水管周围灰质腹外侧区(vLPAG)处GABAA_(α3)及GABAB受体的变化,探讨vLPAG处GABAA_(α3)、GABAB受体在疼痛信号传导中的作用。方法健康清洁级雄性SD大鼠12只,体重280~320g,采用完全随机方法将大鼠分为生理盐水组(NS组)和甲醛组(F组),每组6只。NS组足底注射无菌生理盐水50μl,F组足底注射2%甲醛50μl。每隔5分钟记录1次疼痛评分(PIS评分),每隔10分钟记录1次机械痛阈,每隔15分钟记录1次皮肤厚度、皮肤温度,总观察时间为60min。记录各项指标后处死大鼠,取中脑导水管周围灰质腹外侧区提取蛋白,采用Western blot法检测GABAA_(α3)及GABAB受体含量的变化。结果 F组大鼠注射甲醛后立即出现本模型的典型自发痛行为,各时点PIS评分明显高于NS组(P<0.05),且为典型的两相式。注射后10~60min F组机械痛阈明显低于NS组(P<0.05)。注射后15~60min F组皮肤温度和皮肤厚度明显高于NS组(P<0.05)。F组大鼠GABAA_(α3)及GABAB受体含量明显高于NS组(P<0.05)。结论中脑导水管周围灰质腹外侧区GABAA_(α3)及GABAB受体的表达上调与大鼠急性疼痛条件下痛阈降低有关。

Objective To investigate the role of GABAAaa and GABAB receptors in the ventro- lateral periaqueductal gray in the development of paw acute pain in rats. Methods Twelve male SD rats, weighing 280-320 g, were randomly divided into two groups., normal saline group （group NS）, formaldehyde-induced pain group （group F）, 6 rats in each group. In group F, rats were subcu- taneously injected wkh 2% formaldehyde 50μl into the ventral surface of right hind paw to induce pe- riphery inflammatory pain. In group NS, rats were subcutaneously injected with normal saline into the ventral surface of right hind paw. Mechanical threshold was assessed using von Frey hairs for every ten minutes. The rat pain behavior scores were recorded for every five minutes. The thickness of skin and skin temperature were recorded for every fifteen minutes. Results Mechanical hyperalgesia were induced in group F after formalin injection into right hind paw. Compared with group NS, rat pain be- havior scores were increased significantly in group F at all time points after injection, mechanical threshold were decreased significantly in group F at 10-60 rain after injection, the temperature of the skin and the skin thickness were increased significantly in group F at 15-60 min after injection （P〈 0. 05）, the levels of the expression of GABAAa3 and GABAB were significantly increased in group F （P〈0.05）. Conclusion GABAAa3 and GABAB receptors mediates formalin-induced hyperalgesia at ventrolateral portion of the PAG （vlPAG） of rats.