Rimonabant abolishes sensitivity to workload changes in a progressive ratio procedure

Area of Science:

• Neuroscience
• Behavioral Pharmacology
• Psychopharmacology

Background:

• Marijuana use is linked to amotivational syndrome, characterized by reduced persistence in tasks.
• This syndrome may stem from decreased motivation, particularly for sustained effort.

Purpose of the Study:

• To investigate the effects of Tetrahydrocannabinol (THC) and rimonabant on motivation for food.
• To differentiate their impacts on response persistence under varying effort demands.

Main Methods:

• Dose-effect functions for THC and rimonabant were determined using progressive-ratio (PR) schedules of reinforcement.
• Behavioral economics principles were applied to assess motivation under different workload conditions (PR3, PR5, PR10, PR exponential).

Main Results:

• Both THC and rimonabant decreased response rate and responses per reinforcer on a PR5 schedule.
• Rimonabant reduced session length, while THC did not.
• Under increasing PR schedule demands, rimonabant decreased overall reinforced responses, response rate, and session length.
• THC primarily decreased response rate, showing greater dependence on task workload and duration.

Conclusions:

• Rimonabant consistently reduces food motivation, irrespective of effort.
• THC's effects on food-seeking behavior are more nuanced, influenced by task difficulty and duration.
• These findings differentiate the motivational effects of cannabinoid agonists and antagonists.