Demand for cocaine and food over time

Area of Science:

• Behavioral neuroscience
• Addiction research
• Psychopharmacology

Background:

• The reinforcing strength of essential goods, like food, remains stable with experience.
• Conversely, the reinforcing strength of non-essential goods, such as cocaine, can increase with exposure.
• Understanding these differences is crucial for distinguishing between addictive and non-addictive reinforcers.

Purpose of the Study:

• To investigate whether the change in reinforcing strength with experience differs between abused drugs and biologically necessary goods.
• To determine if time-based changes in essential value can differentiate addictive from non-addictive substances.

Main Methods:

• Experiment 1: Rats (n=5) earned cocaine under a Fixed-Ratio 3 schedule, followed by re-assessment of cocaine demand across Fixed Ratios (3-560).
• Experiment 2: Rats (n=5) had their food demand curves determined, then re-determined using an identical procedure.
• Demand curves were fitted with the exponential model to calculate essential value.

Main Results:

• The second determination of cocaine demand showed a significantly greater essential value than the first, indicating increased strength with exposure.
• Re-determined food demand curves showed no significant change in essential value compared to the initial determination.
• Cocaine's reinforcing strength increased with experience, while food's did not.

Conclusions:

• The study demonstrates that the reinforcing strength of cocaine, an abused drug, increases with experience, unlike that of food.
• Time-dependent changes in essential value can serve as a key metric for differentiating addictive substances from essential goods.
• These findings contribute to understanding the neurobiological basis of addiction.