Sham surgeries for central and peripheral neural injuries persistently enhance pain-avoidance behavior as revealed by an operant conflict test. Issue 11 (November 2019)

• Record Type: Journal Article
• Authors: Odem, Max A.; Lacagnina, Michael J.; Katzen, Stephen L.; Li, Jiahe; Spence, Emily A.; Grace, Peter M.; Walters, Edgar T.
• Is Part Of: Pain. Volume 160:Issue 11(2019)
• Publication Date: 2019-11
• Subjects: Evoked pain -- Affective pain -- Exploratory drive -- Reflex hypersensitivity -- Nociceptors; Pain -- Periodicals; Douleur -- Périodiques; Anesthésie -- Périodiques; Pain; Electronic journals; Periodicals; Electronic journals; 616.0472
• DOI: 10.1097/j.pain.0000000000001642
• Languages: English
• ISSNs: 0304-3959

Abstract

Abstract : Abstract: Studies using rodent models of neuropathic pain use sham surgery control procedures that cause deep tissue damage. Sham surgeries would thus be expected to induce potentially long-lasting postsurgical pain, but little evidence for such pain has been reported. Operant tests of voluntary behavior can reveal negative motivational and cognitive aspects of pain that may provide sensitive tools for detecting pain-related alterations. In a previously described operant mechanical conflict test involving lengthy familiarization and training, rodents freely choose to either escape from a brightly lit chamber by crossing sharp probes or refuse to cross. Here, we describe a brief (2-day) mechanical conflict protocol that exploits rats' innate exploratory response to a novel environment to detect persistently enhanced pain-avoidance behavior after sham surgeries for 2 neural injury models: thoracic spinal cord injury and chronic constriction injury of the sciatic nerve. Pitting the combined motivations to avoid the bright light and to explore the novel device against pain from crossing noxious probes disclosed a conflicting, hyperalgesia-related reluctance to repeatedly cross the probes after injury. Rats receiving standard sham surgeries demonstrated enhanced pain-like avoidance behavior compared with naive controls, and this behavior was similar to that of corresponding chronic constriction injury or spinal cord injury rats weeks or months after injury. In the case of sham surgery for spinal cord injury, video analysis of voluntary exploratory behavior directed at the probes revealed enhanced forepaw withdrawal responses. These findings have important implications for preclinical investigations into behavioral alterations and physiological mechanisms associated with postsurgical and neuropathic pain. Abstract : Reduced voluntary exploration across a noxious substrate revealed persistent, previously unrecognized enhancement of pain-avoidance behavior in rats with sham surgeries for central and peripheral neuropathic pain models.