Gender differences in delay-discounting under mild food restriction.

Area of Science:

• Neuroscience
• Behavioral Science
• Animal Models

Background:

• Impulsivity is a key symptom of attention-deficit hyperactivity disorder (ADHD).
• Delay-discounting tasks in animal models assess impulsivity, but primarily use male subjects under severe food restriction.
• Previous research indicates potential sex differences in impulsivity, warranting further investigation.

Purpose of the Study:

• To investigate sex differences in impulsive behavior using a delay-discounting task in CD-1 mice.
• To examine the effect of mild food restriction on impulsivity in male and female mice.
• To explore the relationship between food restriction levels, sex, and impulsive decision-making.

Main Methods:

• Adult male and female CD-1 mice were maintained at 90% of ad libitum body weight (mild food restriction).
• Mice were tested in operant chambers using a delay-discounting paradigm with immediate (small-soon) and delayed (large-late) food pellet rewards.
• Behavioral data, including choice shifts at increasing delays (0-150s), were analyzed, alongside circadian activity and novelty-seeking tests.

Main Results:

• Two distinct behavioral profiles emerged: "steep" (shifting at short delays) and "flat" (not shifting at long delays).
• "Steep" females demonstrated higher impulsivity by shifting choices at shorter delays compared to "steep" males.
• Females exhibited greater activity in circadian and novelty-seeking tests, suggesting potentially higher exploratory behavior.

Conclusions:

• Under mild food restriction, female mice display significantly higher impulsivity than male mice.
• This finding contrasts with studies using severe food restriction, indicating that the level of food restriction influences observed sex differences in impulsivity.
• Exploratory behavior in females may play a role in delay-discounting tasks, suggesting that task parameters interact with sex and restriction levels to modulate impulsive behavior.