title: Role of the increased noradrenergic neurotransmission in drug self-administration.
abstract: Psychostimulants increase extracellular monoamine concentrations in the CNS. While the contributions of dopamine (DA) and serotonin (5-HT) to the reinforcing effect of psychostimulants have been examined, less is known about the involvement of norepinephrine (NE). In the present study, cocaine, desipramine (DMI) and JZ-III-84 were made available to rhesus monkeys (n=4) responding under a progressive-ratio (PR) schedule. These compounds vary in their in vitro selectivities for blocking NE uptake relative to DA from high (DMI) to modest (JZ-III-84) to non-selective (cocaine). Additionally, cocaine mixed with DMI in mg/kg dose-ratios of 1:1 to 1:3 was made available for self-administration. NE uptake inhibition by the mixture of cocaine and DMI at a ratio of 1:3 was evaluated in an ex vivo uptake assay. Cocaine (0.01-0.1 mg/(kg injection)) and JZ-III-84 (0.001-0.1 mg/(kg injection)) functioned as positive reinforcers with sigmoidal or biphasic dose-response functions, whereas DMI failed to do so. The addition of DMI to cocaine did not systemically alter self-administration of cocaine. In the ex vivo uptake assay, the addition of DMI to cocaine significantly increased the NE uptake inhibition compared to cocaine. These results support the conclusion that CNS NE is not involved in the reinforcing mechanism of psychostimulants.
authors.affiliation: Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, 2500 N. State Street, Jackson, 39216-4505, USA.
authors.forename: Sunmee
authors.initials: S
authors.lastname: Wee
authors.forename: Zhixia
authors.initials: Z
authors.lastname: Wang
authors.forename: Rong
authors.initials: R
authors.lastname: He
authors.forename: Jia
authors.initials: J
authors.lastname: Zhou
authors.forename: Alan P
authors.initials: AP
authors.lastname: Kozikowski
authors.forename: William L
authors.initials: WL
authors.lastname: Woolverton
mesh_terms: D000818:Animals; D000697:Central Nervous System Stimulants / Q000008:administration & dosage*; D003042:Cocaine / Q000008:administration & dosage; D006993:Hypnotics and Sedatives; D008253:Macaca mulatta; D008297:Male; D023421:Models, Animal; D012646:Self Administration; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*
chemical_list: D000697:Central Nervous System Stimulants; D006993:Hypnotics and Sedatives; D003042:Cocaine