Intracerebral self-administration of the cannabinoid receptor agonist CP 55,940 in the rat: Interaction with the opioid system

Daniela Braida, Morena Pozzi, Daniela Parolaro, Mariaelvina Sala

Research output: Contribution to journalArticle

Abstract

The effect of CP 55,940 {(-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4- (3-hydroxypropyl)cyclo-hesanol}, heroin and etonitazene on intracerebroventricular (i.c.v.) self-administration in a free-choice procedure was evaluated in rats. Animals were trained in 1-h daily sessions with a continuous reinforcement schedule to press two active levers to obtain the vehicle of each drug. Then, when a stable baseline was reached, each drug could be self-administered by pressing the lever found to be less preferred during training, while the vehicle came from the other. The number of bar pressings associated with the delivery of increasing unit doses of CP 55,940 (0.1, 0.2, 0.4, 0.8, 1.6 μg/2 μl/infusion), heroin (0.125, 0.25, 0.5, 1, 2 μg/2 μl/infusion) or etonitazene (0.1-0.2-0.5-1 μg/2 μl/infusion) and with the delivery of the corresponding vehicle was fitted by symmetrical parabolas. The mean drug intake was linearly related to the log of self-administered drugs. Pretreatment with SR141716A [N-piperidino-5-(4-chlorophenyl)1-(2,4-dichloro-phenyl)-4-methylpyrazole-3- carboxamide] (0.5 mg/kg) or naloxone HCl (2 mg/kg/i.p.) 15 min before each daily session reduced the self-administration of both CP 55,940 and heroin. The combination of CP 55,940 with heroin or etonitazene reduced the number of drug-associated lever pressings compared to that obtained with the maximal reinforcing unit dose of each drug alone. These findings suggest there may be a strong interaction between opioids and the cannabinoid system.

Original languageEnglish
Pages (from-to)227-234
Number of pages8
JournalEuropean Journal of Pharmacology
Volume413
Issue number2-3
DOIs
Publication statusPublished - Feb 16 2001

Keywords

  • Cannabinoid
  • Free-choice
  • Opiate
  • Self-administration

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience
  • Pharmacology

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