title: The mGlu5 receptor antagonists MPEP and MTEP attenuate behavioral signs of morphine withdrawal and morphine-withdrawal-induced activation of locus coeruleus neurons in rats.
abstract: N-Methyl-D-aspartate (NMDA) antagonists have been demonstrated to suppress the signs of opiate withdrawal; however, side effects limit their clinical use. Since the metabotropic glutamate (mGlu) 5 receptor has been shown to affect glutamate release and modulate NMDA receptor function, we examined the effects of two selective mGlu5 receptor antagonists, 2-methyl-6-(phenyl-ethynyl)-pyridine (MPEP) and 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (MTEP), on morphine withdrawal. Pretreatment with MPEP or MTEP (1, 3, and 10 mg/kg, i.p.) significantly attenuated behavioral signs of morphine withdrawal. Specifically, both MPEP and MTEP attenuated the occurrence/severity of chews, digging, salivation, and weight loss, and increased the occurrence of erections. Neither compound changed the occurrence of wet-dog shakes, ptosis, irritability, or lacrimation. Both MPEP and MTEP produced a modest, but significant, attenuation of morphine-withdrawal-induced activation of locus coeruleus neurons in anesthetized rats. These results indicate a role for mGlu5 receptors in morphine withdrawal and suggest the potential for mGlu5 antagonists in the treatment of withdrawal from opiates and other drugs of abuse.
authors.affiliation: Lilly Research Laboratories, Eli Lilly and Co., Lilly Corporate Center, Indianapolis, IN 46285, USA. rasmussen_kurt@lilly.com
authors.forename: Kurt
authors.initials: K
authors.lastname: Rasmussen
authors.forename: Heidi
authors.initials: H
authors.lastname: Martin
authors.forename: James E
authors.initials: JE
authors.lastname: Berger
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Seager
mesh_terms: D000818:Animals; D008125:Locus Coeruleus / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors*; D013375:Substance Withdrawal Syndrome / Q000188:drug therapy* / Q000378:metabolism / Q000523:psychology; D013844:Thiazoles / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: C472365:3-((2-methyl-1,3-thiazol-4-yl)ethynyl)pyridine; D011725:Pyridines; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; D013844:Thiazoles; D009020:Morphine; C121465:6-methyl-2-(phenylethynyl)pyridine