Nutrient-conditioned intake stimulation does not require a distinctive flavor cue in rats

Area of Science:

• Neuroscience
• Behavioral Science
• Nutritional Science

Background:

• Nutrient intake can be regulated by post-oral signals, influencing appetite and flavor learning.
• Appetition, a process where nutrient presence stimulates intake and preference, is typically studied with flavored solutions paired with nutrient infusions.

Purpose of the Study:

• To investigate if intragastric (IG) maltodextrin (MD) infusions can stimulate intake and preference in rodents without a distinctive flavor cue.
• To determine the role of post-oral nutrient sensing in appetite stimulation and preference conditioning.

Main Methods:

• Rats received either water or a bitter sucrose octaacetate (SOA) solution orally, paired with IG MD infusions.
• Fluid intake was measured over 20-hour periods during training and extinction phases.
• Two-bottle choice tests were used to assess preferences.

Main Results:

• Both groups (SOA and water) significantly increased their total fluid intake (oral + IG) when paired with IG MD infusions.
• Intake decreased during extinction when IG infusions were switched to water.
• Rats previously exposed to SOA paired with IG MD showed a preference for the SOA solution over water when both were paired with IG MD.

Conclusions:

• Intragastric nutrient infusions can stimulate oral intake and condition preferences even in the absence of a distinctive oral flavor cue.
• Post-oral nutrient sensing plays a crucial role in appetition, influencing both intake volume and learned preferences.
• The findings highlight the brain's ability to associate internal nutrient signals with external sensory cues, or lack thereof, to guide feeding behavior.