title: Dopamine D1- and D2-like receptor mechanisms in relapse to cocaine-seeking behavior: effects of selective antagonists and agonists.
abstract: Dopaminergic mechanisms are thought to be critical in mediating relapse to cocaine-seeking behavior. This study examined the different roles of D1- and D2-like receptor mechanisms in the relapse process. Squirrel monkeys were given extended histories of i. v. cocaine self-administration under conditions in which responding was maintained jointly by response-contingent cocaine injections and a cocaine-paired visual stimulus (second-order schedule). Responding was then extinguished by substituting saline for cocaine injections and omitting presentations of the cocaine-paired stimulus. Subsequently, noncontingent priming injections of cocaine combined with restoration of the cocaine-paired stimulus induced dose-dependent reinstatement of drug-seeking behavior, with response rates approaching those maintained by active cocaine self-administration. The priming effects of cocaine were attenuated by several D1- and D2-like receptor antagonists and low efficacy agonists but not by the D3-preferring antagonists UH 232 and AJ-76. The priming effects of cocaine were mimicked by the D2-like receptor agonists R(-)-propylnorapomorphine hydrochloride (NPA) and quinpirole, less consistently by 7-OH-DPAT, and not by the D1-like receptor agonists SKF-81297 and SKF-82958, the D3-preferring agonist PD-128,907, or any low efficacy agonist. Cotreatment with NPA, PD-128,907, and 7-OH-DPAT did not alter reinstatement of drug-seeking behavior induced by a maximally effective priming dose of cocaine, whereas cotreatment with D1-like receptor agonists attenuated the priming effects of cocaine. The results suggest that D1- and D2-like receptors play fundamentally different roles in the relapse process. Although stimulation of D2-like, but probably not D3-like, receptors appears necessary for induction of relapse, either stimulation or blockade of D1-like receptors appears to be inhibitory with respect to relapse.
authors.affiliation: Harvard Medical School, New England Regional Primate Research Center, Southborough, MA 01772-9102, USA.
authors.forename: T V
authors.initials: TV
authors.lastname: Khroyan
authors.forename: R L
authors.initials: RL
authors.lastname: Barrett-Larimore
authors.forename: J K
authors.initials: JK
authors.lastname: Rowlett
authors.forename: R D
authors.initials: RD
authors.lastname: Spealman
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects* / Q000502:physiology; D003042:Cocaine / Q000008:administration & dosage*; D019970:Cocaine-Related Disorders / Q000503:physiopathology*; D003214:Conditioning, Classical; D004195:Disease Models, Animal; D018491:Dopamine Agonists / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000494:pharmacology*; D065127:Dopamine D2 Receptor Antagonists; D008297:Male; D017447:Receptors, Dopamine D1 / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology*; D017448:Receptors, Dopamine D2 / Q000819:agonists / Q000502:physiology*; D012453:Saimiri; D012646:Self Administration
chemical_list: D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D003042:Cocaine