Orally self-administered cocaine: reinforcing efficacy by the place preference method

Area of Science:

• Pharmacology
• Neuroscience
• Behavioral Science

Background:

• Cocaine's reinforcing effects are well-documented.
• Understanding the efficacy of different administration routes is crucial for addiction research.
• Place preference conditioning (PPC) is a standard method for assessing drug reinforcement.

Purpose of the Study:

• To compare the reinforcing efficacy of cocaine administered via intraperitoneal (IP) injection versus oral self-administration.
• To evaluate cocaine's reinforcing effects using both bolus oral doses and schedule-induced oral intake.
• To correlate pharmacokinetic data with observed place preference conditioning.

Main Methods:

• Three separate place preference conditioning (PPC) experiments were conducted with rats.
• Cocaine was administered via IP injection (7.5 mg/kg), oral self-administration bolus (15 mg/kg), or schedule-induced oral drinking (19.1 mg/kg).
• Pharmacokinetic measurements (serum and brain cocaine levels) were performed.

Main Results:

• All three cocaine administration methods (IP, oral bolus, schedule-induced oral) produced significant place preference conditioning in rats.
• The dose-exposure conditions were sufficient to elicit PPC across all experimental groups.
• Cocaine pharmacokinetics in serum and brain correlated with the observed reinforcing efficacy.

Conclusions:

• Intraperitoneal and oral routes of cocaine administration can both establish significant reinforcing effects.
• Oral cocaine self-administration, whether in bolus or schedule-induced forms, demonstrates robust reinforcing properties.
• Pharmacokinetic profiles are key determinants of cocaine's reinforcing efficacy across different administration paradigms.