Pharmacology of conditioned flavor preferences in sham -feeding rats: Effects of opioid and dopaminergic antagonists.
Item
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Title
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Pharmacology of conditioned flavor preferences in sham -feeding rats: Effects of opioid and dopaminergic antagonists.
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Identifier
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AAI3008886
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identifier
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3008886
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Creator
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Yu, Weizhen.
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Contributor
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Adviser: Richard J. Bodnar
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Date
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2001
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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, Experimental | Psychology, Psychobiology
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Abstract
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Relatively little is known about the neurochemical and pharmacological mechanisms involved in flavor preference learning. Since opioid and dopamine systems are both implicated in the response to sweet solutions, the present study examined the dose-dependent abilities of the general opioid antagonist, naltrexone, the D1 antagonist, SCH23390, and the D2 antagonist, raclopride to alter the acquisition and expression of flavor preferences conditioned by the sweet taste of sucrose in sham-feeding rats. This was accomplished by adding a novel flavor (the CS+) to a 16% sucrose solution, and a different flavor (the CS-) to a less-preferred 0.2% saccharin solution. Rats were trained to sham drink these solutions on alternating days, which minimized postingestive actions. Preferences were assessed in two-bottle tests following vehicle or drug treatment. Rats under food-restricted, ad libitum, and water-restricted conditions all displayed significant CS+ preferences in vehicle tests after training. Although naltrexone significantly reduced total intakes during two-bottle, sham-feeding tests, it failed to block the acquisition and expression of the preference for the CS+ flavor over the CS- flavor. Thus, although naltrexone significantly reduces the intake of sweet solutions, it has little or no effect on the acquisition o-r expression of flavor preferences conditioned by sucrose in sham-feeding rats. In stark contrast to the lack of opioid antagonist effects, both the D1 and the D2 antagonists, produced equipotent and dose-dependent reductions in total intake and blocked the expression of CS+ preference. These data indicate that dopaminergic D1 and D 2 receptors play pivotal and functionally equivalent roles in the expression of flavor preferences conditioned by the sweet taste of sucrose. Dopaminergic antagonist (200 nmol/kg) pretreatment during training failed to block the acquisition of flavor preferences in these rats. These data show that both D1 and D2 receptor antagonists block the expression of a sucrose-conditioned preference, but produces substantially lesser effects upon the acquisition of this form of flavor conditioning. Therefore, both D1- and D2-receptor functions are critically involved in the expression of flavor preference conditioned by the sweet taste of sucrose, but both receptor subtypes have a more limited role in the acquisition of this preference.
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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.
