title: Metabotropic glutamate antagonists alone and in combination with morphine:  comparison across two models of acute pain and a model of persistent, inflammatory pain.
abstract: The present study examined the effects of the mGluR1 antagonist JNJ16259685 (JNJ) and the mGluR5 antagonist 2-methyl-6-phenylethynylpyridine (MPEP) alone and in combination with morphine in two acute pain models (hotplate, warm water tail-withdrawal), and a persistent, inflammatory pain model (capsaicin). In the hotplate and warm water tail-withdrawal procedures, JNJ and MPEP were ineffective when administered alone. In both procedures, JNJ potentiated morphine antinociception. In the hotplate procedure, MPEP potentiated morphine antinociception at the highest dose examined, whereas in the warm water tail-withdrawal procedure MPEP attenuated morphine antinociception at a moderate dose and potentiated morphine antinociception at a high dose. For both JNJ and MPEP, the magnitude of this morphine potentiation was considerably greater in the hotplate procedure. In the capsaicin procedure, the highest dose of MPEP produced intermediate levels of antihyperalgesia and also attenuated the effects of a dose of morphine that produced intermediate levels of antihyperalgesia. In contrast, JNJ had no effect when administered alone in the capsaicin procedure and did not alter morphine-induced antihyperalgesia. The present findings suggest that the effects produced by mGluR1 and mGluR5 antagonists alone and in combination with morphine can be differentiated in models of both acute and persistent pain.
authors.affiliation: Behavioral Neuroscience Program, Department of Psychology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3270, USA. mjpicker@email.unc.edu
authors.forename: Mitchell J
authors.initials: MJ
authors.lastname: Picker
authors.forename: Dana
authors.initials: D
authors.lastname: Daugherty
authors.forename: Fredrick E
authors.initials: FE
authors.lastname: Henry
authors.forename: Laurence L
authors.initials: LL
authors.lastname: Miller
authors.forename: Linda A
authors.initials: LA
authors.lastname: Dykstra
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D002211:Capsaicin; D004195:Disease Models, Animal; D004359:Drug Therapy, Combination; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology / Q000627:therapeutic use*; D007249:Inflammation / Q000188:drug therapy; D008297:Male; D009020:Morphine / Q000494:pharmacology / Q000627:therapeutic use*; D009294:Narcotics / Q000627:therapeutic use*; D010146:Pain / Q000139:chemically induced / Q000188:drug therapy*; D010147:Pain Measurement / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology / Q000627:therapeutic use*; D011804:Quinolines / Q000494:pharmacology / Q000627:therapeutic use*; D051381:Rats; D011916:Rats, Inbred F344; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors*
chemical_list: C495417:(3,4-dihydro-2H-pyrano(2,3)b-quinolin-7-yl)-(cis-4-methoxycyclohexyl) methanone; D018691:Excitatory Amino Acid Antagonists; D009294:Narcotics; D011725:Pyridines; D011804:Quinolines; D018094:Receptors, Metabotropic Glutamate; D009020:Morphine; C121465:6-methyl-2-(phenylethynyl)pyridine; D002211:Capsaicin