Objective To investigate the effects of low-intensity ultrasound irradiation on prostaglandins E2 in inflammatory tissues. Methods Twenty-four New Zealand rabbits were randomly divided into the ultrasound irradiation paw group, ultrasound irradiation biceps femoris group, pseudo irradiation group, and normal control group. Except the normal control group, paws of rabbits of other groups were injected with carrageenan solution to establish the inflammatory pain model. Paws of rabbits of the ultrasound irradiation paw group and ipsilateral biceps femoris of rabbits of the ultrasound irradiation biceps femoris group were irradiated with 0.2 MHz ultrasound for 20 min. Rabbits of the pseudo irradiation group were ultrasound were irradiated without power for 20 min. The blood samples were collected from ear artery immediately and 1 h after irradiation. The level of β-endorphin was detected by the ELISA. After the second blood sampling, 10 mg of paw tissue of both hind legs were collected and the level of prostaglandin E2 was detected by the ELISA. Results The level of prostaglandin E2 of the ultrasound irradiation paw group was significantly higher than those of the ultrasound irradiation biceps femoris group, pseudo irradiation group, and the normal control group. The differences of serum levels of β-endorphin of the ultrasound irradiation paw group and ultrasound irradiation biceps femoris group at two time points were not statistically

significant. Conclusion Low-intensity ultrasound irradiation of biceps femoris can improve the serum level of β-endorphin and will not promote the release of prostaglandin E2 in inflammation tissues. It is an ideal method for relieving the inflammatory pain by ultrasound irradiation.