Intra-ventral pallidal glutamate antagonists block expression of morphine-induced place preference.
The role of ionotropic glutamate receptors within the ventral pallidum (VP) in the expression of conditioned place preference (CPP) and motor adaptations to morphine was evaluated. VP-cannulated rats were subjected to 3 days of conditioning in which saline was paired to one distinct chamber in the morning and morphine (8 mg/kg ip or its vehicle) was paired to an alternate chamber in the afternoon. This induced (a) CPP expression in drug-free rats 1 day later, which was blocked by immediate pretreatments with intra-VP injections of a glutamate antagonist cocktail (DL-2-amino-5- phosphonopentanoic acid lithium salt [AP-5] + 6-cyano-7-nitroquinoxaline-2,3-dione disodium salt [CNQX]), and (b) changes in motor function expressed following an acute morphine challenge 18 days later, which were absent if preceded by a 10-day treatment with the glutamate antagonists injected unilaterally once daily in alternating hemispheres. Thus, VP ionotropic glutamate receptors are critical mediators of the expression of place preference and motor adaptations subsequent to repeated morphine exposure.
Dallimore
Jeanine E
JE
Department of Pharmacology and Experimental Therapeutics, Loyola University Chicago, School of Medicine, Maywood, IL 60153-5515, USA.
Mickiewicz
Amanda L
AL
Napier
T Celeste
TC
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology*; D000818:Animals; D001245:Association Learning / Q000187:drug effects / Q000502:physiology; D002755:Choice Behavior / Q000187:drug effects* / Q000502:physiology; D003214:Conditioning, Classical / Q000187:drug effects* / Q000502:physiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D005917:Globus Pallidus / Q000187:drug effects* / Q000502:physiology; D018698:Glutamic Acid / Q000502:physiology*; D007267:Injections; D007274:Injections, Intraperitoneal; D007279:Injections, Subcutaneous; D008297:Male; D011939:Mental Recall / Q000187:drug effects / Q000502:physiology; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017470:Receptors, Glutamate / Q000502:physiology; D017450:Receptors, Opioid, mu / Q000187:drug effects / Q000502:physiology; D012931:Social Environment
D018691:Excitatory Amino Acid Antagonists; D017470:Receptors, Glutamate; D017450:Receptors, Opioid, mu; D018698:Glutamic Acid; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate; D009020:Morphine