title: Striatal dopamine D1 and D2 receptors are differentially regulated following buprenorphine or methadone treatment.
abstract: BACKGROUND
  Chronic administration of morphine induces adaptations in neurotransmission system such as the dopamine pathway, and these modifications could be influenced by the drug administration pattern. Methadone and buprenorphine are the two main opioid substitution therapies, and despite their protracted use in humans, no study has investigated their ability to regulate dopamine system after chronic exposure/withdrawal.
  
  
  OBJECTIVE
  We evaluated the consequences of two administration patterns of methadone and buprenorphine on striatal dopamine D1 (D1R) and D2 (D2R) receptor levels.
  
  
  METHODS
  Mice were treated with escalating doses of methadone or buprenorphine for 5 days either once daily (binge) or three times a day (TTD). D1R and D2R density in striatum was measured by autoradiography using [(3)H]-SCH23390 and [(3)H]-raclopride, respectively, at 1 (WD1), 14 (WD14), and 35 (WD35) days after the last opioid injection.
  
  
  RESULTS
  A downregulation of D1R was observed upon TTD administration of buprenorphine and binge methadone treatment while an increase of those receptor levels was detected both with binge buprenorphine and TTD methadone treatments. Concerning the D2R, we rather measured an early or late downregulation with both agonists and administration patterns.
  
  
  CONCLUSIONS
  Our results demonstrated that methadone and buprenorphine were able to differentially regulate dopamine receptor density depending on the withdrawal period and the administration pattern.
authors.affiliation: Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8206, Paris, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Allouche
authors.forename: Thierry
authors.initials: T
authors.lastname: Le Marec
authors.forename: Antoine
authors.initials: A
authors.lastname: Coquerel
authors.forename: Florence
authors.initials: F
authors.lastname: Noble
authors.forename: Nicolas
authors.initials: N
authors.lastname: Marie
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage*; D000818:Animals; D002047:Buprenorphine / Q000008:administration & dosage*; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D008297:Male; D008691:Methadone / Q000008:administration & dosage*; D051379:Mice; D017447:Receptors, Dopamine D1 / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000378:metabolism*
chemical_list: D000701:Analgesics, Opioid; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D002047:Buprenorphine; D008691:Methadone