Role of the nucleus accumbens in the mediation of opioid-induced feeding in rats.
Item
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Title
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Role of the nucleus accumbens in the mediation of opioid-induced feeding in rats.
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Identifier
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AAI9986369
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identifier
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9986369
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Creator
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Ragnauth, Andre K.
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Contributor
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Adviser: Richard J. Bodnar
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Date
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2000
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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
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Abstract
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Although multiple (mu, delta and kappa) opioid agonists and antagonists respectively induce and reduce feeding in rats, questions are raised about the nature of their interactions. The nucleus accumbens (NAcc), particularly its shell region, and ventral tegmental area (VTA), particularly its dopaminergic projection, are reciprocally-connected structures are implicated in food intake. The first study examined whether general, mu, mu1 or kappa opioid antagonists in the NAcc shell blocked feeding induced by deprivation, glucoprivation and palatability. Whereas general, mu and kappa antagonists significantly decreased deprivation and glucoprivic feeding, general and mu opioid antagonists significantly decreased sucrose intake, establishing the NAcc shell in the opioid mediation of these feeding models. A second study examined VTA involvement in these feeding responses following general, mu, kappa, delta 1 or delta2 antagonism. Only high doses of general and delta 2 antagonists in the VTA significantly decreased these forms of intake, demonstrating site-specificity.;To examine whether specific or multiple receptor subtype antagonists mediated opioid agonist-induced feeding, a third study determined whether feeding elicited by selective mu (DAMGO), delta1 (DPDPE) and delta2 (deltorphin) agonists in the NAcc shell were blocked by general, mu, mu1, kappa1, delta1 and delta2 opioid antagonists. Significant reductions were noted for feeding induced by DAMGO (mu, delta2 and kappa1 antagonists) and DPDPE (mu, delta1, delta2 and kappa1 antagonists) in the NAcc shell, yet deltorphin-induced feeding was unaffected by delta2 antagonism, and augmented by both mu and kappa opioid antagonists. Thus, the pattern of multiple receptor subtype antagonism in the NAcc upon feeding is dependent upon the selective agonist. To test VTA dopaminergic modulation of opioid-induced feeding in the NAcc, a last study examined whether feeding elicited by DAMGO or deltorphin in the NAcc shell was blocked by D1 or D2 receptor antagonists Feeding induced by DAMGO, but not deltorphin in the NAcc was significantly reduced by D1, but not D2 antagonism, indicating only minor dopaminergic mediation of NAcc opioid-induced feeding. These data firmly establish the NAcc, and secondarily the VTA, as putative sites of action at which opioid peptides and their receptors act to modulate feeding under a wide variety of ingestive conditions.
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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.
