A rat model of postoperative pain.

Research on pain resulting from an incision is crucial for developing therapies for postoperative pain, a condition for which effective and inexpensive treatments are not yet available. Because of the gap between preclinical models of persistent pain (e.g., inflammatory, neuropathic) and acute postsurgical pain, efforts have been undertaken to develop methods for studying pain caused by incisions. To this end, a rat model for postoperative pain has been developed. The model uses a plantar incision in the hindpaw and is characterized by persistent, reduced withdrawal thresholds to mechanical stimuli, as is the case in patients after surgery. The pain behaviors are greatest immediately after recovery from anesthesia. The enhanced responsiveness remains remarkable for several days and then gradually decreases. The model is useful for screening test compounds that may be effective in reducing postoperative pain and for understanding pain mechanisms associated with incisions.