A single in vivo exposure to cocaine abolishes endocannabinoid-mediated long-term depression in the nucleus accumbens

J Neurosci. 2004 Aug 4;24(31):6939-45. doi: 10.1523/JNEUROSCI.0671-04.2004.

Abstract

In the nucleus accumbens (NAc), a key structure to the effects of all addictive drugs, presynaptic cannabinoid CB1 receptors (CB1Rs) and postsynaptic metabotropic glutamate 5 receptors (mGluR5s) are the principal effectors of endocannabinoid (eCB)-mediated retrograde long-term depression (LTD) (eCB-LTD) at the prefrontal cortex-NAc synapses. Both CB1R and mGluR5 are involved in cocaine-related behaviors; however, the impact of in vivo cocaine exposure on eCB-mediated retrograde synaptic plasticity remains unknown. Electrophysiological and biochemical approaches were used, and we report that a single in vivo cocaine administration abolishes eCB-LTD. This effect of cocaine was not present in D1 dopamine receptor (D1R) -/- mice and was prevented when cocaine was coadministered with the selective D1R antagonist 8-chloro-2,3,4,5-tetrahydro-3-5-1h-3-benzazepin-7-ol (0.5 mg/kg) or with the NMDA receptor (NMDAR) blocker (+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate (1 mg/kg), suggesting the involvement of D1R and NMDAR. We found that the cocaine-induced blockade of retrograde signaling was correlated with enhanced expression levels of Homer scaffolding proteins containing the coiled-coil domain and accompanied by a strong reduction of mGluR5 surface expression. The results suggest that cocaine-induced loss of eCB retrograde signaling is caused by a reduction in the ability of mGluR5 to translate anterograde glutamate transmission into retrograde eCB signaling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cannabinoid Receptor Modulators / metabolism*
  • Carrier Proteins / metabolism
  • Cocaine / pharmacology
  • Cocaine-Related Disorders / physiopathology*
  • Electrophysiology
  • Endocannabinoids*
  • Homer Scaffolding Proteins
  • Immunoblotting
  • Mice
  • Neuronal Plasticity / drug effects*
  • Neuronal Plasticity / physiology
  • Nucleus Accumbens / metabolism*
  • Receptor, Cannabinoid, CB1
  • Receptor, Metabotropic Glutamate 5
  • Receptors, Dopamine D1
  • Receptors, Metabotropic Glutamate
  • Receptors, N-Methyl-D-Aspartate
  • Synaptic Transmission / drug effects
  • Synaptic Transmission / physiology

Substances

  • Cannabinoid Receptor Modulators
  • Carrier Proteins
  • Endocannabinoids
  • Grm5 protein, mouse
  • Homer Scaffolding Proteins
  • Receptor, Cannabinoid, CB1
  • Receptor, Metabotropic Glutamate 5
  • Receptors, Dopamine D1
  • Receptors, Metabotropic Glutamate
  • Receptors, N-Methyl-D-Aspartate
  • Cocaine