Behavioral dependence on caffeine and phencyclidine in rhesus monkeys: interactive effects

Area of Science:

• Behavioral Neuroscience
• Psychopharmacology
• Animal Models

Background:

• Phencyclidine (PCP) is a dissociative drug with abuse potential.
• Caffeine is a widely consumed stimulant with known physiological and behavioral effects.
• Understanding drug interactions and withdrawal effects is crucial for addiction research.

Purpose of the Study:

• To investigate the effects of caffeine withdrawal on operant behavior maintained by food, water, and phencyclidine (PCP) in rhesus monkeys.
• To examine potential interactive effects between PCP and caffeine withdrawal on behavior.
• To assess the sensitivity of operant baselines to drug discontinuation.

Main Methods:

• Rhesus monkeys self-administered PCP and water under fixed-ratio schedules.
• Caffeine was added to food pellets, and its effects were studied during withdrawal.
• PCP was removed and reinstated, with and without concurrent caffeine administration.

Main Results:

• Caffeine withdrawal significantly reduced food-maintained responding, with recovery over 7 days.
• Water and PCP intake were not systematically disrupted by caffeine withdrawal.
• Behavioral disruptions were more severe when PCP was removed during concurrent caffeine withdrawal, suggesting an interaction.

Conclusions:

• Disruptions in operant behavior serve as sensitive indicators of caffeine access termination.
• Behavioral disruptions from caffeine withdrawal are less severe than those from PCP withdrawal.
• Combined PCP and caffeine withdrawal may produce interactive behavioral effects.