A Novel Method Utilizing Approach-avoidance To Assess The Aversive Nature Of Pain
Harris, Amber Leeann
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Pain is a multidimensional experience that involves sensory, emotional/affective, and evaluative components, yet preclinical pain research has mainly focused on testing the sensory dimension. Those suffering from pain may be confronted with complex emotional conflicts on a daily basis in which they are presented with the dilemma of choosing to satiate other motivational drives or attend to their pain. Preclinical assessments focusing on sensory mechanisms and measurements may be lacking in predictive validity for treating pain populations. Some paradigms to test the affective nature of pain in laboratory rodents have been validated, yet they focus on escape from pain. Organisms may not be able to choose to escape pain if they want to satiate other homeostatic drives, such as hunger. Therefore, the objective of this research was to develop a new paradigm for testing the aversive nature of preclinical pain models in rodents by presenting contending motivational drives of hunger and pain.Subjects were presented with an operant box approach-avoidance conflict in which they had the choice to experience pain to obtain a reward and more specifically, they indicated whether pressing a lever associated with stimulation in a paw with a neuropathic or inflammatory condition was preferred. Results indicated there was no statistical preference when neuropathic and inflammatory conditions were presented simultaneously, and there was also a suppression in reward seeking behavior, which coincides with previous research. However, in contrast with what was expected, control groups with pain conditions in only one paw also displayed no statistical lever/stimulation preference. This may be explained by a generalization effect caused by the proximity of the levers. After the levers were separated to opposite sides of the chamber, there was still a generalization effect in the group with one painful paw and one unaffected paw on test day one. Subjects were not able to effectively discriminate distinct outcomes for each lever/paw. By the second test day, there was an emerging trend towards preferring stimulation in the unaffected paw. For this reason, this paradigm may present an opportunity to investigate learning and memory mechanisms in pain. Comparisons made between the validated escape-avoidance paradigm and the approach-avoidance paradigm indicate that the two measures may engage different mechanisms. Future research will aim to investigate: the utility of measuring the suppression of reward seeking in a one lever paradigm, learning and memory in a two lever paradigm, and neural correlates for approach-avoidance measures in pain.