Clonidine antagonizes the aversive effects of opiate withdrawal and the rewarding effects of morphine only in opiate withdrawn rats.
The researchers asked whether clonidine, an alpha 2-noradrenergic agonist, would block selectively the motivational effects of opiate withdrawal and whether clonidine's effects would respect the boundary between nondeprived and deprived motivational states. In a place conditioning paradigm, clonidine (0.05 mg/kg ip) blocked the rewarding effects of morphine in opiate-withdrawn rats (as well as the aversive properties of withdrawal itself), but did not affect morphine place preferences (2 and 20 mg/kg) in drug-naive rats. Furthermore, clonidine blocked the acquisition of morphine (15 mg/kg), but not LiCl (15 mg/kg), conditioned taste aversions in water-deprived rats. The results suggest that the motivational system activated in deprived animals includes dopaminergic and noradrenergic components that are in series with each other.
Nader
K
K
Department of Anatomy and Cell Biology, University of Toronto, Canada. K. nader@utoronoto.ca
van der Kooy
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D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D001143:Arousal / Q000187:drug effects* / Q000502:physiology; D001245:Association Learning / Q000187:drug effects / Q000502:physiology; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology; D003000:Clonidine / Q000494:pharmacology*; D003214:Conditioning, Classical / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D018021:Lithium Chloride / Q000494:pharmacology; D008297:Male; D011939:Mental Recall / Q000187:drug effects / Q000502:physiology; D009020:Morphine / Q000494:pharmacology*; D009021:Morphine Dependence / Q000503:physiopathology*; D009042:Motivation; D009638:Norepinephrine / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012931:Social Environment; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology*; D013649:Taste / Q000187:drug effects / Q000502:physiology
D000316:Adrenergic alpha-Agonists; D009020:Morphine; D018021:Lithium Chloride; D003000:Clonidine; D009638:Norepinephrine