Establishment Of A Murine Model Of Breakthrough Pain By Heat Stimulation

Objective:To establish a murine model of breakthrough pain by heat stimulation, and evaluate the model.Methods:1.Establish a bone cancer pain C57BL/6mouse model based on our previous study[13]. Cultivate and inoculate Lewis Lung Carcinoma cells into the mouse left femur. Due to previous pain evaluation results, we choose the14th day after the inoculation to perform our experiments.2.Choose appropriate morphine dosage for analgesia. With Morphine injection (I.P.) in the mice with bone cancer at two different levels of doses (3mg/kg and6mg/kg) and von Frey test, here we find out the relationship between morphine doses, dosing time and pain thresholds.3.Then with adequately pain-control morphine dosing, a contact heat stimulation at55℃for20s on the tumor to induce breakthrough pain and establish a breakthrough pain model, and von Frey test, behavioral observation and hindpaw usage scoring were carried out. Data were analyzed with statistic tests.Results:1.Bone cancer pain model was successfully produced, according to previous study by Huang Dong[13].2.Both3mg/kg and6mg/kg morphine dosages can provide analgesia for the bone cancer mice, but6mg/kg morphine dosage can provide pain relief in shorter time and offer a better time-window for the following heat stimulation.3.Breakthrough pain model was initially established. Von Frey test, pain behavioral observation and hindpaw usage scoring showed that, in a short period of time after heat stimulation, pain threshold decreased sharply, typical pain behavioral changes were obtained and hindpaw usage score lowering. Data analysis showed results were with great significance (p<0.05).Conclusion:1.Based on successfully produced bone cancer pain model,6mg/kg morphine dosage can provide adequate analgesia and better time-window for bone cancer pain mice to be stimulated by heat. 2.Through pain threshold test, behavioral observation and hindpaw usage scoring, we can prove that a contact heat stimulation at55℃for20s can induce breakthrough pain on bone cancer pain mice.