Karen Ackroff

Publications (80) View all

• Article: WITHDRAWN: Post-oral glucose stimulation of intake and conditioned flavor preference in C57BL/6J mice: A concentration-response study.

  Steven Zukerman, Karen Ackroff, Anthony Sclafani
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  ABSTRACT: This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.
  Physiology & Behavior 11/2012; · 2.87 Impact Factor
• Article: Post-oral glucose stimulation of intake and conditioned flavor preference in C57BL/6J mice: A concentration-response study.

  Steven Zukerman, Karen Ackroff, Anthony Sclafani
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  ABSTRACT: In a recent study, intragastric (IG) self-infusion of 16% glucose stimulated 1-h intake and conditioned a preference for a flavored saccharin solution in C57BL/6J mice (Zukerman et al., 2011). Experiment 1 of the present study presents a concentration-response analysis of IG glucose-induced intake stimulation monitored by recording licking response every min of the 1h/day sessions. Separate groups of food-restricted mice consumed a flavored saccharin solution (the CS-) paired with IG self-infusions of water (Test 0) followed by a different flavored solution (the CS+) paired with IG self-infusions of 2, 4, 8, 16, or 32% glucose (Tests 1-3). Following additional CS- and CS+ training sessions, a two-bottle CS+ vs. CS- choice test was conducted without infusions. Self-infusions of 8%, 16% or 32% glucose stimulated CS+ licking within 12min of the first test session and even earlier in subsequent test sessions, and also conditioned significant CS+ preferences in the two-bottle test. The stimulation of early licking and CS+ preference increased as a function of glucose concentration. The amount of glucose solute self-infused increased with sugar concentration as did post-infusion blood glucose levels. The 2% glucose infusion did not stimulate CS+ intake and the 2% and 4% infusions failed to produce a CS+ preference in the 1-h test. Experiment 2 revealed that intraperitoneal self-infusions of 8% glucose, unlike IG glucose self-infusions, failed to stimulate CS+ licking or preference despite producing maximal increases in blood glucose levels. Taken together, these and other findings suggest that glucose rapidly produces concentration-dependent intestinal signals that stimulate intake and condition flavor preferences while postoral satiation signals limit total amounts consumed.
  Physiology & Behavior 11/2012; · 2.87 Impact Factor
• Article: MSG intake and preference in mice are influenced by prior testing experience.

  Karen Ackroff, Rachel Weintraub, Anthony Sclafani
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  ABSTRACT: Monosodium glutamate (MSG), the prototypical umami substance, is used as a flavor enhancer in many foods, but when presented alone is often only weakly attractive. Yet with experience mice will develop strong preferences for MSG solution over water. The present experiments explored the conditions that change indifference to preference for MSG. C57BL/6J mice were given a series of 2-day two-bottle tests with water vs. an ascending series of MSG concentrations (0.1-450mM) to assess preference and intake. Naive mice were indifferent to all concentrations, but following forced one-bottle exposure to 300mM MSG they preferred most concentrations and consumed more MSG. Exposure to 100mM MSG also increased subsequent MSG preference but not intake. Experience with other nutritive solutions (8% sucrose, 8% Polycose, 8% casein hydrolysate, and isocaloric 3.5% soybean oil emulsion) also enhanced subsequent MSG preference and intake. Polycose and sucrose experience were almost as effective as MSG experience. However, not all sapid solutions were effective; 0.8% sucralose and 10mM MSG exposure did not alter subsequent MSG preference. The generality of the preexposure effect was tested by offering an ascending series (0.1-100mM) of inosine monophosphate (IMP), another umami substance; initial indifference was converted to preference after forced exposure to 300mM MSG. Together these results suggest that a combination of oral and post-oral effects may be responsible for the experience effect, with MSG itself the most potent stimulus. A final experiment revealed that MSG preference in naïve mice is enhanced by presenting the MSG and water drinking spouts far apart rather than side by side. Thus the preferences for umami solutions in mice are subject to influence from prior tastant experience as well spout position, which should be taken into account when studying acceptance of taste solutions in mice.
  Physiology & Behavior 07/2012; 107(2):207-17. · 2.87 Impact Factor
• Article: Role of gut nutrient sensing in stimulating appetite and conditioning food preferences.

  Anthony Sclafani, Karen Ackroff
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  ABSTRACT: The discovery of taste and nutrient receptors (chemosensors) in the gut has led to intensive research on their functions. Whereas oral sugar, fat, and umami taste receptors stimulate nutrient appetite, these and other chemosensors in the gut have been linked to digestive, metabolic, and satiating effects that influence nutrient utilization and inhibit appetite. Gut chemosensors may have an additional function as well: to provide positive feedback signals that condition food preferences and stimulate appetite. The postoral stimulatory actions of nutrients are documented by flavor preference conditioning and appetite stimulation produced by gastric and intestinal infusions of carbohydrate, fat, and protein. Recent findings suggest an upper intestinal site of action, although postabsorptive nutrient actions may contribute to flavor preference learning. The gut chemosensors that generate nutrient conditioning signals remain to be identified; some have been excluded, including sweet (T1R3) and fatty acid (CD36) sensors. The gut-brain signaling pathways (neural, hormonal) are incompletely understood, although vagal afferents are implicated in glutamate conditioning but not carbohydrate or fat conditioning. Brain dopamine reward systems are involved in postoral carbohydrate and fat conditioning but less is known about the reward systems mediating protein/glutamate conditioning. Continued research on the postoral stimulatory actions of nutrients may enhance our understanding of human food preference learning.
  AJP Regulatory Integrative and Comparative Physiology 03/2012; 302(10):R1119-33. · 3.34 Impact Factor
• Article: Flavor preferences conditioned by intragastric glucose but not fructose or galactose in C57BL/6J mice.

  Anthony Sclafani, Karen Ackroff
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  ABSTRACT: The present study determined if mice, like rats, differ in their flavor conditioning responses to intragastric (IG) infusions of three common monosaccharide sugars. In Experiment 1, C57BL/6J mice were trained to drink a flavored saccharin solution (the CS+) paired with intragastric (IG) self-infusions of 16% glucose, fructose or galactose and a different flavored solution (the CS-) paired with IG water infusions during 22 h/day training sessions. The glucose infusions increased CS+ intakes during training and produced a strong CS+ preference (~87%) in two-bottle choice tests. In contrast, the fructose and galactose infusions reduced CS training intakes and did not condition a CS+ preference. Experiment 2 determined if reducing fructose and galactose concentration would enhance conditioning. However, IG infusions of 8% sugar also failed to condition CS+ preferences. The robust conditioning response to IG glucose confirms results obtained with rats, but the indifference of mice to IG fructose and galactose contrasts with preference and avoidance responses observed in rats. The effectiveness of glucose to condition preferences suggests an important role for glucose-specific sensors rather than gut "sweet" taste receptors in the postoral modulation of carbohydrate appetite.
  Physiology & Behavior 03/2012; 106(4):457-61. · 2.87 Impact Factor