title: Dopamine uptake inhibitors but not dopamine releasers induce greater increases in motor behavior and extracellular dopamine in adolescent rats than in adult male rats.
abstract: Most life-long drug addiction begins during adolescence. Important structural and functional changes in brain occur during adolescence and developmental differences in forebrain dopamine systems could mediate a biologic vulnerability to drug addiction during adolescence. Studies investigating age differences in psychostimulant responses have yielded mixed results, possibly because of different mechanisms for increasing extracellular dopamine. Recent research from our laboratory suggests that adolescent dopamine systems may be most affected by selective dopamine uptake inhibitors. We investigated age-related behavioral responses to acute administration of several dopamine uptake inhibitors [methylphenidate, 1-{2-[bis-(4-fluorophenyl)methoxy]ethyl}-4-(3-phenylpropyl)piperazine (GBR12909), and nomifensine] and releasing agents [amphetamine and methylenedioxymethamphetamine (MDMA)] in adolescent and adult male rats. Methylphenidate and amphetamine effects on stimulated dopamine efflux were determined using fast-scan cyclic voltammetry in vivo. Dopamine uptake inhibitors but not dopamine releasing agents induced more locomotion and/or stereotypy in adolescent relative to adult rats. MDMA effects were greater in adults at early time points after dosing. Methylphenidate but not amphetamine induced much greater dopamine efflux in periadolescent relative to adult rats. Periadolescent male rats are particularly sensitive to psychostimulants that are DAT inhibitors but are not internalized and do not release dopamine. Immaturity of DAT and/or DAT associated signaling systems in adolescence specifically enhances behavioral and dopaminergic responses in adolescence.
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Q David
authors.initials: QD
authors.lastname: Walker
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Morris
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Arrant
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Nagel
authors.forename: Sarah
authors.initials: S
authors.lastname: Parylak
authors.forename: Guiying
authors.initials: G
authors.lastname: Zhou
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Caster
authors.forename: Cynthia M
authors.initials: CM
authors.lastname: Kuhn
mesh_terms: D000375:Aging / Q000502:physiology*; D000662:Amphetamines / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001923:Brain Chemistry / Q000187:drug effects; D004298:Dopamine / Q000378:metabolism*; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology*; D004594:Electrophysiology; D008297:Male; D008774:Methylphenidate / Q000494:pharmacology; D009043:Motor Activity / Q000187:drug effects*; D018817:N-Methyl-3,4-methylenedioxyamphetamine / Q000494:pharmacology; D017072:Neostriatum / Q000187:drug effects / Q000378:metabolism; D009627:Nomifensine / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000662:Amphetamines; D018765:Dopamine Uptake Inhibitors; D010879:Piperazines; D009627:Nomifensine; D008774:Methylphenidate; C043425:vanoxerine; D018817:N-Methyl-3,4-methylenedioxyamphetamine; D004298:Dopamine