A rat model for studying electroacupuncture analgesia on acute visceral hyperalgesia

The aim of this study was to establish an appropriate rat model to study the effect of electroacupuncture (EA) analgesia on acute visceral hyperalgesia. Adult rats received colorectal instillation with different concentrations of acetic acid (AA). Treatment with EA was performed for 30 min at bilateral acupoints of ST-36 and ST-37 in the hind limbs. The visceral sensation of all rats was quantified by scores of abdominal withdrawal reflex (AWR) and discharges of rectus abdominis electromyogram (EMG) in response to colorectal distension (CRD). Two hours after instillation of saline (no AA), 1%, 2%, and 4% AA, there were no, slight, moderate and severe visceral hyperalgesia, respectively. Application of EA significantly relieved the visceral hyperalgesia induced by 2% but not 4% AA. The results suggest that 2% AA acute visceral hyperalgesia in adult rats responds well to EA treatment. This may offer an appropriate model for the investigation of EA effects.