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Published on: June 27, 2014
Flavor preferences conditioned by postingestive effects of nutrients in preweanling rats
Kevin P Myers1, Jennifer Ferris, Anthony Sclafani
1Department of Psychology, Bucknell University, Lewisburg, PA 17837, United States. kmyers@bucknell.edu
Insights
Young rats can learn flavor-nutrient associations before weaning, influencing later food preferences. This nutrient conditioning demonstrates early learning capabilities in preweanling rats.
Area of Science:
- Neuroscience
- Animal Behavior
- Nutritional Science
Background:
- Adult rats exhibit flavor-nutrient learning.
- Understanding early learning mechanisms is crucial for developmental science.
Purpose of the Study:
- To determine if preweanling rats can associate flavors with postingestive nutrient effects.
- To investigate if these associations influence post-weaning flavor preferences.
Main Methods:
- Preweanling rats received intraoral infusions of flavors paired with glucose or saccharin.
- Post-weaning, rats chose between previously learned flavors.
- Experiments involved intraoral and intragastric nutrient infusions.
Main Results:
- Rats preferred flavors previously paired with glucose over those paired with saccharin.
- Rats preferred flavors associated with nutrient infusions over control flavors.
- Preference for flavor-nutrient associations developed over time after weaning.
Conclusions:
- Neural mechanisms for flavor-nutrient associations are present before weaning in rats.
- Early life experiences, including flavors from maternal milk, can shape dietary preferences.
- Nutrient conditioning is an important factor in early dietary learning.
Abstract:
The purpose of these experiments was to determine if preweanling rats, like adults, are capable of learning to associate an arbitrary flavor with the postingestive effects of nutrients, and then demonstrate a preference for that flavor after weaning. In Experiment 1, preweanlings were trained daily from postnatal day (P) 16 through P19 with intraoral (IO) infusions of a grape or cherry flavor (CS+) mixed with 20% glucose (US), and the opposite flavor (CS-) mixed with 0.05% saccharin. After weaning, rats were given a 4-h two-bottle choice between the CS+ and CS- flavors both presented in 0.05% saccharin. Rats preferred the flavor previously paired with glucose. In Experiment 2 using similar methods, rats learned to prefer a flavor (CS+G) paired with a glucose US over a flavor (CS+S) paired with a sweeter but less nutritive sucrose US, indicating involvement of postingestive reinforcement. In Experiment 3 preweanling rats with IO and intragastric (IG) catheters were trained with a CS+ flavor paired with IG nutrient infusion, and a CS- flavor paired with no IG infusion. These rats showed no flavor preference 3 days after weaning, but did significantly prefer the CS+ flavor over the CS- flavor 10 days after weaning. Together these experiments demonstrate that neural mechanisms for flavor-nutrient associations are developed before weaning, allowing young rats to learn associations between arbitrary flavors and nutritive consequences. Thus nutrient conditioning may be one way that early experience (such as flavors from the maternal diet transmitted in milk) influences later dietary preferences.
