Flavor preferences conditioned by sucrose depend upon training and testing methods: two-bottle tests revisited

Area of Science:

• Behavioral Neuroscience
• Sensory Science
• Animal Behavior

Background:

• Prior research indicated rats preferred a less sweet flavor (CS5) over a sweeter flavor (CS30) when both were presented at an intermediate concentration.
• This preference was hypothesized to result from conditioned satiety to the CS30 flavor, but equal intakes in some tests did not fully support this.
• The role of sweetness differences between training and testing solutions in flavor preference was not fully understood.

Purpose of the Study:

• To investigate the influence of altered sweetness context between training and testing on flavor preference in rats.
• To determine if changes in the post-ingestive reinforcing actions of sucrose solutions affect conditioned flavor preferences.
• To clarify the mechanisms underlying conditioned flavor preferences in response to varying sucrose concentrations.

Main Methods:

• Rats were trained with flavored sucrose solutions (5% and 30%) paired with intragastric infusions to create net concentrations.
• Two-bottle preference tests were conducted using intermediate or varied sucrose concentrations during training and testing phases.
• Flavor preferences were assessed by measuring the intake of different flavored solutions under controlled conditions.

Main Results:

• Rats initially showed no preference between flavors when tested with an intermediate sucrose concentration after training with differential net concentrations.
• Following further training, rats developed a significant preference for the CS30 flavor over the CS5 flavor under specific infusion conditions.
• Flavor preference was strongly influenced by the sucrose concentration used during two-bottle tests, with a preference for CS5 in 30% sucrose and CS30 in 5% sucrose.

Conclusions:

• The sweetness context of test solutions significantly impacts conditioned flavor preferences in rats.
• Changes in the post-ingestive reinforcing effects, influenced by sweetness, play a crucial role in flavor preference.
• Findings highlight the importance of considering the testing solution's properties when interpreting conditioned flavor reward studies.