The role of acetylcholine neurotransmission in the ventral tegmental area on food reward and food -related learning.
Item
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Title
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The role of acetylcholine neurotransmission in the ventral tegmental area on food reward and food -related learning.
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Identifier
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AAI3214529
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identifier
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3214529
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Creator
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Sharf, Ruth.
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Contributor
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Adviser: Robert Ranaldi
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Date
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2006
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Language
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English
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Publisher
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City University of New York.
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Subject
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Psychology, Psychobiology | Psychology, Behavioral
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Abstract
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The following dissertation is an investigation of the role of acetylcholine neurotransmission in the ventral tegmental area (VTA) in food reward and food-related learning. The role of VTA acetylcholine in food-rewarded operant conditioning, or lever-pressing to obtain a food-reward, was investigated. Here, during training, animals learn about a novel food stimulus, environment, and motoric response. Rats were trained to lever-press under a fixed ratio schedule of food reinforcement. Bilateral intra-VTA scopolamine (a muscarinic acetylcholine receptor, or mAChR, antagonist) or mecamylamine (a nicotinic acetylcholine receptor, or nAChR, antagonist) microinjections were administered prior to and following training. All rats that received the mecamylamine doses, and those that received the scopolamine vehicle dose, demonstrated daily increases in lever pressing until asymptote levels were reached, at which point these maximal levels were maintained. Those rats that had initially received an active dose of scopolamine during training failed to show daily increases until scopolamine treatment was terminated. Scopolamine and mecamylamine administration following training failed to affect responding. These results suggest that mAChR, but not nAChR, are necessary for acquiring a food-rewarded lever-pressing task, but neither are necessary for the performance of the task. The role of VTA acetylcholine in feeding-related learning was examined. Here, animals were presented with a novel food-stimulus in a novel environment in which they learn to feed. Here, scopolamine, but not mecamylamine, treatment prevented daily increases in pellet consumption and both compounds failed to reduce consumption after the feeding-task was acquired (i.e., after demonstration of stable responding). These results suggest that mAChR, but not nAChR, are necessary for the acquisition, but not the expression, of feeding-related learning. The role of acetylcholine neurotransmission in food-related motivation, or in the amount of "work" an animal will perform to obtain a food-reward, was investigated. Here, neither scopolamine nor mecamylamine significantly affected lever-pressing. These results suggest that neither mAChR nor nAChR stimulation is necessary for the motivation to obtain a food reward in fully trained animals. Altogether, these data suggest a functional role of VTA mAChR in the acquisition of food-related learning but not in the expression of previously acquired behaviors.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
