title: D1- and D2-like dopamine receptors in the CA1 region of the hippocampus are involved in the acquisition and reinstatement of morphine-induced conditioned place preference.
abstract: The hippocampus plays a vital role in processing contextual memories and reward related learning tasks, such as conditioned place preference (CPP). Among the neurotransmitters in the hippocampus, dopamine is deeply involved in reward-related processes. This study assessed the role of D1- and D2-like dopamine receptors within the CA1 region of the hippocampus in the acquisition and reinstatement of morphine-CPP. To investigate the role of D1 and D2 receptors in morphine acquisition, the animals received different doses of D1- and/or D2-like dopamine receptor antagonists (SCH23390 and sulpiride, respectively) into the CA1, 5min before the administration of morphine (5mg/kg, subcutaneously) during a 3-days conditioning phase. To evaluate the involvement of these receptors in morphine reinstatement, the animals received different doses of SCH23390 or sulpiride (after extinction period) 5min before the administration of a low dose of morphine (1mg/kg) in order to reinstate the extinguished morphine-CPP. Conditioning scores were recorded by Ethovision software. The results of this study showed that the administration of SCH23390 or sulpiride, significantly decreased the acquisition of morphine-CPP. Besides, the injection of these antagonists before the administration of a priming dose of morphine, following the extinction period, decreased the reinstatement of morphine-CPP in sacrificed rats. However, the effect of sulpiride on the acquisition and reinstatement of morphine-CPP was more significant than that of SCH23390. These findings suggested that D1- and D2-like dopamine receptors in the CA1 are involved in the acquisition and reinstatement of morphine-CPP, and antagonism of these receptors can reduce the rewarding properties of morphine.
authors.affiliation: Department of Pharmacology & Toxicology, Faculty of Pharmacy, Pharmaceutical Sciences Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Nasim
authors.initials: N
authors.lastname: Assar
authors.affiliation: Department of Pharmacology & Toxicology, Faculty of Pharmacy, Pharmaceutical Sciences Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Dorna
authors.initials: D
authors.lastname: Mahmoudi
authors.affiliation: Substance Abuse and Dependence Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Farhoudian
authors.affiliation: Substance Abuse and Dependence Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran.
authors.forename: Mohammad Hasan
authors.initials: MH
authors.lastname: Farhadi
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Fatahi
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Electronic address: Haghparast@yahoo.com.
authors.forename: Abbas
authors.initials: A
authors.lastname: Haghparast
mesh_terms: D000818:Animals; D001552:Benzazepines / Q000008:administration & dosage; D056547:CA1 Region, Hippocampal / Q000187:drug effects* / Q000502:physiology*; D003214:Conditioning, Classical / Q000187:drug effects*; D065127:Dopamine D2 Receptor Antagonists / Q000008:administration & dosage; D005108:Extinction, Psychological / Q000187:drug effects; D008297:Male; D009020:Morphine / Q000008:administration & dosage*; D017208:Rats, Wistar; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors / Q000502:physiology*; D017448:Receptors, Dopamine D2 / Q000502:physiology*; D013469:Sulpiride / Q000008:administration & dosage
chemical_list: D001552:Benzazepines; D065127:Dopamine D2 Receptor Antagonists; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; C534628:SCH 23390; D009020:Morphine; D013469:Sulpiride
keywords: Acquisition; Conditioned place preference; D1-like dopamine receptor; D2-like dopamine receptor; Hippocampus; Reinstatement