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Nicotine competition with light control of conditioned responding
Environmental stimuli that co-occur with tobacco use can come to evoke drug-related conditioned responses (CRs) that facilitate use and relapse. In that situation, nicotine serves as an unconditioned stimulus (US). Recent research has shown that nicotine can also function as a conditional stimulus (CS) for non-drug USs prompting the question of whether the CS properties of nicotine can compete with the environmental CSs for conditioned excitation. In beginning to address this question, the past nicotine CS training procedure was modified. Previous work had used a subcutaneous injection as a contextual CS paired with multiple deliveries of sucrose. The current dissertation established that 1-sec intravenous (IV) infusions of nicotine can serve as a CS for brief access to sucrose. Tests with mecamylamine and hexamethonium confirmed that the central effects of nicotine were responsible for responding, and an Unpaired control confirmed that temporal contiguity was necessary for development of the CR. Competition between nicotine and a discrete exteroceptive light CS was then examined. Overshadowing, in which one element of a compound CS controls more of the CR than the other element, and blocking, in which previous conditioning to one element of a CS prevents conditioned responding evoked by a second, subsequently added element of a compound CS, were evaluated as part of this dissertation. After being trained as a compound CS, nicotine (0.03 mg/kg/infusion) and the light evoked a similar level of conditioned responding when tested separately. Nicotine overshadowed the light CS as shown by reduced control of conditioned responding compared to controls. Similarly, when nicotine was trained as the CS and light was added to form the compound CS, subsequent tests revealed blocking of the light by the previous training with the nicotine. Use of a post-hoc control group also showed that the light can block conditioned responding evoked by the nicotine. These results may help inform tobacco cessation therapy by extending the properties of the nicotine CS to include modification of exteroceptive stimuli.^
Biology, Neuroscience|Psychology, Psychobiology|Psychology, Behavioral
Murray, Jennifer Eilene, "Nicotine competition with light control of conditioned responding" (2009). ETD collection for University of Nebraska - Lincoln. AAI3360161.