Conditioned Flavor Preferences: Evaluating Postingestive Reinforcement by Nutrients

Karen Ackroff1, Anthony Sclafani1

1 Brooklyn College of the City University of New York, Brooklyn, New York
Publication Name:  Current Protocols in Neuroscience
Unit Number:  Unit 8.6F
DOI:  10.1002/0471142301.ns0806fs05
Online Posting Date:  May, 2001
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Abstract

The acceptance of food and the expression of preferences for particular foods have both innate and learned components. To determine the mechanism(s) responsible for the acquisition of learned preferences and the enhancement of inborn taste preferences, it is important to separate the component stimuli: the oral flavor cues and the postingestive nutrient cues that are associated with the flavors. Unambiguous analysis of postingestive reinforcement of a nutrient requires postā€oral presentation of the nutrient during or after oral intake of the flavor stimulus. This protocol concentrates on controlling stimulus presentation in associative conditioning, pairing a flavor with positive postingestive effects.

     
 
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Table of Contents

  • Conditioned Flavor Preferences: Evaluating Postingestive Reinforcement by Nutrients
  • Basic Protocol 1: Evaluation of Conditioned Flavor Preferences
  • Alternate Protocol 1: An Automated System for Evaluating Conditioned Flavor Preferences
  • Reagents and Solutions
  • Commentary
  • Literature Cited
  • Figures
     
 
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Materials

Basic Protocol 1: Evaluation of Conditioned Flavor Preferences

  Materials
  • Intragastric catheter (i.g.)–implanted rats: adult female or male rats implanted with subcutaneous 0.04‐in.‐i.d. Silastic intragastric catheter externalized to head or neck with 20‐G stainless steel tubing [to connect to infusion tubing (Davis and Campbell, ); headcap and button connectors available from Instech and Plastics One]
  • 0.2% (w/v) saccharin (prepare with tap water and store covered up to 1 week at room temperature)
  • Flavored saccharin solutions (see recipe)
  • Nutrient solution: 8% (w/w) glucose solution (see recipe) or an emulsion or liquid diet that can be pumped through tubing
  • 10% (v/v) bleach
  • 50‐ or 100‐ml glass or Nalgene drinking bottles with 1‐ml graduations (or 50‐ml conical centrifuge tubes, or 100‐ml plastic graduated cylinders trimmed to remove pour spout and base)
  • Test cages (24 cm wide × 23 cm deep × 30 cm high) with slotted top for passage of infusion tubing, and hardware to hold two drinking bottles upright
  • Single‐hole rubber stoppers to fit drinking bottles (e.g., no. 5 for 50‐ml, no. 5½ for 100‐ml) with curved stainless steel sipper tubes
  • Syringe pumps rated at 1.5 to 2 ml/min (e.g., Razel Scientific Products model A‐99)
  • 20‐ or 30‐ml plastic syringes with blunt 20‐G Luer‐Lok tips
  • Plastic infusion tubing (0.03‐in. i.d. Tygon Microbore tubing; Fisher)
  • Animal balance (±1 g)

Alternate Protocol 1: An Automated System for Evaluating Conditioned Flavor Preferences

  • Lickometer system including sensing circuit, signal amplification, and interface to computer
  • Computer with software for responding to lick inputs with pump activation (see discussion of processing, below)
  • Single‐ or dual‐channel infusion swivel (for long sessions)
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Figures

Videos

Literature Cited

   Ackroff, K. and Sclafani, A. 1994. Flavor preferences conditioned by intragastric infusions of dilute Polycose solutions. Physiol. Behav. 55:957‐962.
   Ackroff, K., Sclafani, A., and Axen, K.V. 1997. Diabetic rats prefer glucose‐paired flavors over fructose‐paired flavors. Appetite 28:73‐83.
   Boakes, R.A. and Lubart, T. 1988. Enhanced preference for a flavour following reversed flavour glucose pairing. Q. J. Exp. Psychol. 40:49‐62.
   Booth, D.A. 1985. Food‐conditioned eating preferences and aversions with interoceptive elements: Conditioned appetites and satieties. Ann. N.Y. Acad. Sci. 443:22‐41.
   Capaldi, E.D. 1990. Hunger and conditioned flavor preferences. In Taste, Experience and Feeding. (E.D. Capaldi and T.L. Powley, eds.) pp. 157‐169. American Psychological Association, Washington, D.C.
   Capaldi, E.D. 1993. Conditioned food preferences. In The Psychology of Learning and Motivation, Vol. 28 (D. Medin, ed.) pp. 1‐33. Academic Press, New York.
   Capaldi, E.D. 1996. Conditioned food preferences. In Why We Eat What We Eat: The Psychology of Eating (E.D. Capaldi, ed.) pp. 53‐80. American Psychological Association, Washington, D.C.
   Davis, J.D. and Campbell, C.S. 1975. Chronic intrajugular, intraportal, gastric, and duodenal cannulae for the rat. In Physiological Techniques in Behavioral Research (D. Singh and D.D. Avery, eds.) pp.163‐177. Brooks Cole, Monterey, Calif.
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   Drucker, D.B., Ackroff, K., and Sclafani, A. 1993. Flavor preference produced by intragastric polycose infusions in rats using a concurrent conditioning procedure. Physiol. Behav. 54:351‐355.
   Drucker, D.B., Ackroff, K., and Sclafani, A. 1994. Nutrient‐conditioned flavor preference and acceptance in rats: Effects of deprivation state and nonreinforcement. Physiol. Behav. 55:701‐707.
   Elizalde, G. and Sclafani, A. 1990a. Flavor preferences conditioned by intragastric polycose: A detailed analysis using an electronic esophagus preparation. Physiol. Behav. 47:63‐77.
   Elizalde, G. and Sclafani, A. 1990b. Fat appetite in rats: Flavor preferences conditioned by nutritive and non‐nutritive oil emulsions. Appetite 15:189‐197.
   Fedorchak, P.M. and Bolles, R.C. 1987. Hunger enhances the expression of calorie‐ but not taste‐mediated conditioned flavor preferences. J. Exp. Psychol. Anim. Behav. Proc. 13:73‐79.
   Galef, B.G., Jr. 1996. Social influences on food preferences and feeding behaviors of vertebrates. In Why We Eat What We Eat: The Psychology of Eating (E.D. Capaldi, ed.) pp. 207‐231. American Psychological Association, Washington, D.C.
   Gibson, E.L. and Booth, D.A. 1988. Fenfluramine and amphetamine suppress dietary intake without affecting learned preferences for protein or carbohydrate cues. Behav. Brain Res. 30:25‐29.
   Gibson, E.L. and Booth, D.A. 1989. Dependence of carbohydrate‐conditioned flavor preference on internal state in rats. Learn. Motiv. 20:36‐47.
   Giza, B.K., Ackroff, K., McCaughey, S.A., Sclafani, A., and Scott, T.R. 1997. Preference conditioning alters taste responses in the nucleus tractus solitarius of the rat. Am. J. Physiol. 273:R1230‐R1240.
   Grill, H.J. and Berridge, K.C. 1985. Taste reactivity as a measure of the neural control of palatability. Prog. Psychobiol. Physiol. Psychol. 11:1‐61.
   Le Magnen, J. 1959. Effets des administrations post‐prandiales de glucose sur l'établissement des appétits. C. R. Séances Soc. Biol. Fil. 153:212‐215.
   Lucas, F. and Sclafani, A. 1989. Flavor preferences conditioned by intragastric fat infusions in rats. Physiol. Behav. 46:403‐412.
   Lucas, F. and Sclafani, A. 1996a. Capsaicin attenuates feeding suppression but not reinforcement by intestinal nutrients. Am.J. Physiol. 270:R1059‐R1064.
   Lucas, F. and Sclafani, A. 1996b. Carbohydrate‐conditioned odor preferences in rats. Behav. Neurosci. 109:446‐454.
   Lucas, F. and Sclafani, A. 1996c. The composition of the maintenance diet alters flavor‐preference conditioning by intragastric fat infusions in rats. Physiol. Behav. 60:1151‐1157.
   Mehiel, R. and Bolles, R.C. 1984. Learned flavor preferences based on caloric outcome. Anim. Learn. Behav. 12:421‐427.
   Mehiel, R. and Bolles, R.C. 1988. Learned flavor preferences based on calories are independent of initial hedonic value. Anim. Learn. Behav. 16:383‐387.
   Pérez, C., Lucas, F., and Sclafani, A. 1995. Carbohydrate, fat and protein condition similar flavor preferences in rats using an oral‐delay procedure. Physiol. Behav. 57:549‐554.
   Pérez, C., Ackroff, K., and Sclafani, A. 1996. Carbohydrate‐ and protein‐conditioned flavor preferences: Effects of nutrient preloads. Physiol. Behav. 59:467‐474.
   Puerto, A., Deutsch, J.A., Molina, F., and Roll, P. 1976. Rapid discrimination of rewarding nutrient by the upper gastrointestinal tract. Science 192:485‐487.
   Ramirez, I. 1985. Oral stimulation alters digestion of intragastric oil meals in rats. Am. J. Physiol. 248:R459‐R463.
   Ramirez, I. 1994. Stimulation of fluid intake by carbohydrates: Interaction between taste and calories. Am. J. Physiol. 266:R682‐R687.
   Sclafani, A. 1990. Nutritionally based learned flavor preferences in rats. In Taste, Experience, and Feeding (E.D. Capaldi and T.L. Powley, eds.) pp. 139‐156. American Psychological Association, Washington, D.C.
   Sclafani, A. 1991. Conditioned food preferences. Bull. Psychon. Soc. 29:256‐260.
   Sclafani, A. 1995. How food preferences are learned—laboratory animal models. Proc. Nutr. Soc. 54:419‐427.
   Sclafani, A. and Ackroff, K. 1994. Glucose‐ and fructose‐conditioned flavor preferences in rats: Taste versus postingestive conditioning. Physiol. Behav. 56:339‐405.
   Sclafani, A. and Lucas, F. 1996. Abdominal vagotomy does not block carbohydrate‐conditioned flavor preferences in rats. Physiol.Behav. 60:447‐453.
   Sclafani, A. and Nissenbaum, J. 1988. Robust conditioned flavor preference produced by intragastric starch infusion in rats. Am. J. Physiol. 255:R672‐R675.
   Spector, A. Andrews‐Labenski, J., and Letterio, F.C. 1990. A new gustometer for psychophysical taste testing in the rat. Physiol. Behav. 47:795‐803.
   Tordoff, M.G. and Friedman, M.I. 1986. Hepatic portal glucose infusions decrease food intake and increase food preference. Am. J. Physiol. 251:R192‐R196.
   Watson, E.A., Simons, E.A., Martinson, F.A., Horn, C.C., and Mitchell, J.C. 1994. High fat‐moderate carbohydrate diet increases flavor preference conditioned with intragastric fat infusion in rats. Soc. Neurosci. Abst. 20:1224.
   Zahorik, D.M., Maier, S.F., and Pies, R.W. 1974. Preferences for flavors paired with recovery from thiamine deficiency in rats: Appetitive conditioning or learned safety? Comp. Physiol. Psychol. 87:1083‐1091.
Key References
   Booth, 1985. See above.
  Describes Booth's earlier work in both animal and human studies.
   Capaldi, 1993. See above.
  Summarizes studies focused on the role of deprivation in preference conditioning.
   Sclafani, 1995. See above.
  A summary of the author's conditioning studies, with a discussion of other methods for enhancing flavor preferences.
   Tordoff, M.G. 1991. Metabolic basis of learned food preferences. In Chemical Senses, Vol.4: Appetite and Nutrition (M.I. Friedman, M.G. Tordoff, and M.R. Kare, eds.) pp.239‐260. Mercel Dekker, New York.
  Summarizes work on the metabolic factors that influence flavor preference learning.
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