The present study describes a new test of tonic pain in rats which can be used as an animal model of persistent pain. In the first experiment, the response to subcutaneous injection of various doses of bee venom into the hind paw of the rat was quantified. The second experiment investigated the effect of morphine and aspirin on the response to an intermediate dose of bee venom. Finally, the third experiment examined the response to concurrent injections of bee venom and formalin. Subcutaneous injection of bee venom produced local inflammation, marked edema, and tonic pain responses. Increasing doses of bee venom produced higher mean pain scores and increased durations of responding. Pain responses lasted up to approximately one hour and the inflammation and edema were virtually gone by 8 hours with the lower doses of bee venom tested and by 2 days with the two highest doses tested. 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 responses similar to formalin alone, with an increased duration of responding at higher intensities. The data suggest that the bee venom test is a valid animal model of experimental tonic pain.

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