The site and mechanism of postingestive carbohydrate reinforcement detection in flavor preference conditioning.
Item
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Title
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The site and mechanism of postingestive carbohydrate reinforcement detection in flavor preference conditioning.
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Identifier
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AAI3232020
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identifier
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3232020
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Creator
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Yiin, Yeh-Min Emma.
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Contributor
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Adviser: Anthony Sclafani
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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, Experimental
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Abstract
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This dissertation research examined the involvement of pre-absorptive and post-absorptive sites in mediating flavor preference conditioning by carbohydrates in rats. Preference conditioning was conducted in rats presented with one arbitrary flavor (conditioned stimulus, CS+) paired with post-oral glucose infusions (unconditioned stimulus, US) and another arbitrary flavor (CS-) paired with post-oral saline or water infusions. Flavor preference was then conducted with a CS+ vs. CS- two-bottle test without infusions. In Experiment 1 the CS+ flavor was paired with glucose infused into the liver via a hepatic portal catheter (10% glucose, 10 ml/2 h). The rats did not develop a CS+ flavor preference. In Experiment 2, 18% sucrose was added to the CS+ and CS-solutions to provide some pre-absorptive nutrient stimulation. The rats still did not prefer the CS+ flavor paired with the hepatic-portal glucose infusion. In Experiment 3 glucose was infused into the small intestine via an intraduodenal (ID) catheter. The glucose (10 ml of 10%) was infused at the same rate as in Experiments 1 and 2 (0.083 mL/min) or at a faster rate (0.18 mL/min). Both rates of ID glucose infusion conditioned a significant CS+ preference. The reinforcement produced by ID glucose infusion was further investigated in Experiment 4 using phlorizin to block the sodium-dependent glucose transporter (SGLT-1) and sensor (SGLT-3). Phlorizin treatment during conditioning reduced CS+ intake during the subsequent flavor test but did not block the expression of a CS+ preference. In Experiment 5, rats were trained with a CS+ flavor paired with ID phlorizin infusion (without glucose) and a CS- flavor paired with ID water infusion. The CS- was preferred to the CS+ in the two-bottle test indicating that phlorizin by itself had an aversive effect. Taken together, the findings indicate that the small intestine is a crucial site for post-ingestive flavor preference conditioning by glucose and suggest that glucose sensors other than SGLT-1 and SGLT-3 are involved. The available evidence, however, does not exclude the involvement of the liver in flavor conditioning by glucose.
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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.
