mGlu5 receptor and protein kinase C implicated in the development and induction of neuropathic pain following chronic ethanol consumption

Eur J Pharmacol. 2007 May 21;562(3):208-11. doi: 10.1016/j.ejphar.2007.01.091. Epub 2007 Feb 16.

Abstract

The central mechanisms of neuropathic pain following chronic ethanol consumption are poorly understood. We previously reported that the levels of metabotropic glutamate 5 (mGlu5) receptor and phosphorylated-protein kinase C (PKC) were significantly increased in the spinal cord following chronic ethanol consumption. The aim of this study was to investigate whether mGlu5 receptor and PKC inhibitors directly attenuate the neuropathic pain-like state induced by chronic ethanol treatment in rats. A significant decrease in the mechanical nociceptive threshold was observed 5 weeks of chronic ethanol consumption. This hyperalgesia was significantly attenuated by repeated i.p. injection of (S)-2,6-diamino-N-[[1-(oxotridecyl)-2-piperidinyl]methyl] hexanamide dihydrochloride (NPC15437), a selective PKC inhibitor, once a day for a week after 4 weeks of ethanol treatment. Furthermore, this hyperalgesia was also significantly attenuated by repeated i.p. injection of 6-methyl-2-[phenylethynyl]-pyridine (MPEP), a selective mGlu5 receptor inhibitor, once a day for a week after 4 weeks of ethanol treatment. Furthermore, the hyperalgesia that developed after 5 weeks of ethanol treatment was significantly suppressed by a single i.p. post-injection with either NPC15437 or MPEP. These findings constitute direct evidence that spinal mGlu5 receptor and PKC play substantial roles in the development and maintenance of an ethanol-dependent neuropathic pain-like state in rats.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alcoholic Neuropathy / chemically induced
  • Alcoholic Neuropathy / physiopathology*
  • Analysis of Variance
  • Animals
  • Central Nervous System Depressants / adverse effects*
  • Ethanol / adverse effects*
  • Hyperalgesia / chemically induced
  • Hyperalgesia / physiopathology
  • Male
  • Neuralgia / chemically induced
  • Neuralgia / physiopathology
  • Nociceptors / drug effects
  • Nociceptors / physiopathology
  • Pain / chemically induced
  • Pain / physiopathology
  • Pain Measurement
  • Pain Threshold / drug effects
  • Protein Kinase C / drug effects*
  • Protein Kinase C / metabolism
  • Rats
  • Rats, Inbred F344
  • Receptor, Metabotropic Glutamate 5
  • Receptors, Metabotropic Glutamate / drug effects*
  • Receptors, Metabotropic Glutamate / metabolism
  • Reflex / drug effects
  • Reflex / physiology

Substances

  • Central Nervous System Depressants
  • Receptor, Metabotropic Glutamate 5
  • Receptors, Metabotropic Glutamate
  • Ethanol
  • Protein Kinase C