切口痛大鼠脊髓兴奋性和抑制性氨基酸类神经递质释放的动态变化

目的 探讨切口痛大鼠脊髓兴奋性和抑制性氨基酸类神经递质释放的动态变化.方法 雄性SD大鼠,麻醉后切开寰枕膜置人环形微透析导管至腰大池.恢复5 d后,选择12只无神经症状的大鼠,随机分为2组(n=6):对照组(C组)仅吸入1.2%异氟醚,切口痛组(Ⅰ组)吸入1.2%异氟醚后制备右后足底切口痛模型.于术前、术后3 h、1 d、2 d、3 d收集各组微透析液并观察大鼠痛行为学,测定微透析液内氨基酸类神经递质浓度.结果 与基础值比较,Ⅰ组天冬氨酸和谷氨酸水平于术后3 h升高(P＜0.01),术后1 d即恢复到基础值水平(P＞0.05),甘氨酸和γ-氨基丁酸的浓度于术后1 d升高(P＜0.01),术后2 d即恢复到基础值水平(P＞0.05),累积疼痛评分于术后3 h、1 d、2 d升高(P＜0.01);与C组比较,Ⅰ组术后3 h天冬氨酸和谷氨酸水平升高,术后1 d甘氨酸和γ-氨基丁酸水平升高,术后3 h、1 d、2 d累积疼痛评分升高(P＜0.01).结论 术后疼痛期脊髓氨基酸类神经递质释放的变化规律具有时间特异性,兴奋性氨基酸类神经递质在切口痛早期释放增加,介导术后早期脊髓敏化的发生;抑制性氨基酸类神经递质迟于兴奋性氨基酸类神经递质的释放,减轻术后疼痛.

Dynamic changes in excitatory and inhibitoty amino acid neurotransmitter release in the spinal cord in a rat model of incisional pain

Objective To examine the dyllamic changes in excitatory and inhibitory amino acid neurotransmitter release in the spinal cord in a rat model of incisional pain.Methods Twelve healthy adult male SD rats weighing 250-300g were anesthetized with intraperitoneal chloral hydrate 300 mg/kg.A loop microdialysis catheter was implanted into the subarachnoid space via the atlanto-occipital membrane and advanced for 8.5 cm candad until lumbar region.The animals were randomly divided into 2 groups(n=6 each): control group(C) and incisional pain group(I).Incisional pain was produced by the plantar incision in the tight hindpaw under 1.2% isoflurane in group I while group C received only anesthesia with 1.2% isoflurane.The microdialysis samples were collected before incision(To,baseline)at 3 h,1 d,2 d and 3 d after incision(T1-4) for determination of amino acid using HPLC.The pain behavior was assessed and scored (O=no pain,2=severe pain) at the above time paints.Results In group I the aspartate and glutamate concentrations in the microdialysis samples were significantly increased at 3 h after incision(T1) as compared with the baseline value at To and returned to the baseline level at l d(T2);the glyeine and r-amino butyric acid concentrations were signifieantly increased at ld (T2)and returned to the baseline level at 2 d(T3).The cumulated pain scores were significantly increased at 3 h,1 d and 2 d after incision and returned to baseline level at 3 d (T4) in group I.Conclusion The increased release of excitatory amino acid neurotransmitter in the early phase after incision may be involved in hyperalgesia while the increased release of inhibitory amino acid neurotransmitter in the later phase may be involved in the pain relief.