改良大鼠牙髓电刺激疼痛模型的研究

目的建立改良大鼠下切牙牙髓电刺激疼痛模型，并评价该模型的应用价值。方法用体积分数为3%戊巴比妥钠腹腔注射麻醉大鼠22只，剥离黏骨膜，暴露下颌骨和下切牙。用特细牙钻针在釉牙骨质界根方处和与其相距1.5 mm的下颌骨处分别钻孔，将细绝缘不锈钢电极置入牙髓腔内，打结固定，用聚羧酸锌黏固粉封固电极与牙体之间部分。刺激电极穿过两孔从两耳间皮肤切口穿出，用丙烯酸树脂固定。动物清醒后，测定电刺激痛阈，评价此模型痛阈的稳定性和辣椒辣素对它的影响。结果22只大鼠全部建模成功，手术后1～2 h清醒，置入电极持续有效时间达6周，局部未见炎症反应。6周后牙髓组织学检查正常，无坏死形态学改变。无论是300 min内多次测定或1、2、3、4周末测定的痛阈值变异系数均小于15%；用此模型能准确测定辣椒辣素镇痛作用的量- 效关系和时- 效关系。结论此种改良大鼠牙髓电刺激疼痛模型制作方法简便，成功率高，电刺激痛阈稳定，适用于在动物清醒状态下评价药物的镇痛作用。

Evaluation on improved tooth pulp electrical stimulation rat model

Objective To improve tooth pulp electrical stimulation rat model to study analgesic effect of drugs.Methods Expose lower mandible and incisor and isolate them with rubber dam,two holes with distance 1.5 mm were drilled below the cemento-enamel junction by a thin diamond bur in 22 adult male rats anesthetized with sodium pentobarbital.A pair of insulated stainless stimulating electrodes were inserted through the holes and knotted to fix them.Drilled holes were filled with zinc polycarboxylate cement.Finally,the stimulating electrodes were directed to the top of the skull.Pain threshold of rats was determined by an electrical stimulator under awake,free conditions to evaluate the stability of the model and the analgesic effect of drugs.Results A valid tooth pulp pain model were set up successfully in 22 rats.Rats regain consciousness at 1 to 2 hours after operation.The inserted electrodes keep efficiency for 6 weeks.Neither tissue morphology change nor inflammation cell infiltration can be found in tooth pulp after 6 weeks under the light microscope.Threshold voltages remained constant under the repeat electric stimulations within 300 min(P>0.05,CV<15%)until 4 weeks(P>0.05,CV<15%).The dose-dependent and time-dependent analgesic effects of capsaicin were showed in this model.Conclusion The improved tooth pulp electrical stimulation rat model is easily performed and shows constant electrical stimulation-induced pain threshold and is suitable for research on analgesic effect of drugs.