The Role of Peripheral Afferent Input in Cancer-Induced Ongoing Bone Pain and Movement-Induced Incident Pain
PublisherThe University of Arizona.
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AbstractCancer-induced bone pain is described as persistent, dull pain that increases in intensity with disease progression. Cancer patients experience ongoing pain and breakthrough pain, defined as transient periods of moderate to severe pain that break through ongoing pain medication. A better understanding of differences in mechanisms driving these aspects of cancer-induced pain may lead to development of more effective pain therapeutics with fewer side effects than currently used treatments. To address this issue, we have developed a preclinical rat model where breast cancer cells are injected in the right tibia of female rats, allowing for cancer growth, metastases, and subsequent bone degradation as revealed by radiographic analyses. To measure ongoing pain, we adapted the conditioned placed preference (CPP) paradigm, which uses negative reinforcement to determine the rewarding aspects of pain alleviating manipulations. A conditioned placed avoidance (CPA) paradigm was used to measure movement-induced incident pain. Our data indicate that peripheral nerve block alleviates cancer-induced ongoing pain, revealing that afferent input maintains ongoing pain. Palpation of the tumor-bearing limb produces CPA, likely reflecting movement-induced breakthrough pain as observed in cancer patients. Such results contribute to the overall goal of developing better therapeutics, thereby improving the quality of life for cancer patients.
Degree ProgramHonors College