Metabotropic glutamate 5 receptor blockade may attenuate cocaine self-administration by decreasing brain reward function in rats

Paul J. Kenny, Benjamin Boutrel, Fabrizio Gasparini, George F. Koob, Athina Markou

Research output: Contribution to journalArticlepeer-review

133 Scopus citations

Abstract

Rationale: Evidence is accumulating that metabotropic glutamate 5 (mGlu5) receptors play an important role in regulating the reinforcing actions of drugs of abuse. Objectives: We examined the effects of the mGlu5 receptor antagonist MPEP on cocaine consumption and cocaine-enhanced brain reward function in rats. Methods: Cocaine consumption was measured in rats with 1 h (short-access; ShA) or 6 h (long-access; LgA) daily access to intravenous cocaine (0.25 mg/infusion) self-administration. Cocaine-enhanced brain reward function was measured by cocaine-induced lowering of intracranial self-stimulation (ICSS) thresholds. Results: Cocaine consumption remained stable and unaltered over successive self-administration sessions in ShA rats. In contrast, cocaine consumption progressively "escalated" in LgA rats. MPEP (1-9 mg/kg) dose-dependently decreased responding similarly in ShA and LgA rats. These data suggest that mGlu5 receptors regulate the reinforcing properties of cocaine, and that this action of mGlu5 receptors is independent of the escalation in consumption associated with extended access to cocaine self-administration. MPEP doses (1-9 mg/kg) that decreased cocaine self-administration elevated brain reward thresholds to a similar degree in cocaine- and vehicle-treated rats, indicating that MPEP induced a negative affective state. The additive effects of MPEP and cocaine on thresholds resulted in attenuation of the magnitude of cocaine-induced (10 mg/kg) lowering of ICSS thresholds. Conclusions: Overall, mGlu5 receptors appear to play an important role in regulating cocaine consumption, and also in regulating brain reward function. Further, it is likely that blockade of mGlu5 receptors may attenuate cocaine consumption, at least in part, by decreasing the baseline activity of brain reward circuitries.

Original languageEnglish
Pages (from-to)247-254
Number of pages8
JournalPsychopharmacology
Volume179
Issue number1
DOIs
StatePublished - Apr 2005
Externally publishedYes

Keywords

  • Addiction
  • Cocaine
  • Dependence
  • Escalation
  • Glutamate
  • Intracranial self-stimulation
  • Metabotropic glutamate 5 (mGlu5) receptor
  • Rat
  • Reward
  • Self-administration

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