The bee venom test: a new tonic-pain test.

The present study describes a new test of tonic pain to be used as an animal model of persistent pain. First, pain responses and edema produced by subcutaneous injection of increasing doses of honey bee venom into the hind paw of the rat were quantified. Second, the effect of morphine and aspirin on the pain responses was investigated. Finally, the response to concurrent injections of bee venom and formalin was examined. Subcutaneous injection of bee venom produced local inflammation, tonic-pain responses lasting from 10 min to more than 1 h, and marked edema lasting from 3 h to more than 48 h. Increasing doses of bee venom produced higher mean pain scores and increased durations of responding. The time course of the edema did not follow the time course of the pain responses. Analgesia was produced by morphine and aspirin, indicating that the bee venom test can be used to test analgesic drugs. Concurrent administration of bee venom and formalin produced pain responses similar to formalin alone, with a less profound interphase depression and a longer duration. The data suggest that the bee venom test is a valid animal model of experimental tonic pain.