Behavioral effects of chronically administered cocaine in squirrel monkeys

Area of Science:

• Pharmacology
• Behavioral Neuroscience
• Drug Addiction Research

Background:

• Cocaine is a potent psychostimulant with a high potential for abuse.
• Understanding the long-term effects of chronic cocaine exposure is crucial for addiction research.
• Previous studies have shown complex behavioral adaptations to chronic stimulant administration.

Purpose of the Study:

• To investigate the development of tolerance or sensitization to the behavioral effects of chronic cocaine administration in squirrel monkeys.
• To assess how chronic cocaine exposure alters acute responses to the drug.

Main Methods:

• Squirrel monkeys were infused with cocaine (0.1 or 0.3 mg/kg/h) for 14 days using osmotic minipumps.
• Behavioral effects were assessed using a fixed-interval schedule of stimulus-shock termination.
• Acute cocaine effects were evaluated using a cumulative-dosing procedure before, during, and after chronic infusion.

Main Results:

• Chronic low-dose cocaine (0.1 mg/kg/h) increased response rates in some subjects.
• Chronic high-dose cocaine (0.3 mg/kg/h) led to tolerance in gross behavioral effects and rate-suppressing effects.
• Acute cocaine administration produced similar effects on schedule-controlled responding regardless of chronic exposure duration or dose.

Conclusions:

• Squirrel monkeys develop tolerance to some behavioral effects of chronic high-dose cocaine.
• No evidence of behavioral sensitization or tolerance to acute cocaine effects was observed during or after chronic administration.
• These findings highlight the complex interplay between chronic and acute cocaine exposure on behavior.