title: Cocaine Self-Administration Produces Long-Lasting Alterations in Dopamine Transporter Responses to Cocaine.
abstract: Cocaine addiction is a debilitating neuropsychiatric disorder characterized by uncontrolled cocaine intake, which is thought to be driven, at least in part, by cocaine-induced deficits in dopamine system function. A decreased ability of cocaine to elevate dopamine levels has been repeatedly observed as a consequence of cocaine use in humans, and preclinical work has highlighted tolerance to cocaine's effects as a primary determinant in the development of aberrant cocaine taking behaviors. Here we determined that cocaine self-administration in rats produced tolerance to the dopamine transporter-inhibiting effects of cocaine in the nucleus accumbens core, which was normalized following a 14 or 60 d abstinence period; however, although these rats appeared to be similar to controls, a single self-administered infusion of cocaine at the end of abstinence, even after 60 d, fully reinstated tolerance to cocaine's effects. A single cocaine infusion in a naive rat had no effect on cocaine potency, demonstrating that cocaine self-administration leaves the dopamine transporter in a "primed" state, which allows for cocaine-induced plasticity to be reinstated by a subthreshold cocaine exposure. Further, reinstatement of cocaine tolerance was accompanied by decreased cocaine-induced locomotion and escalated cocaine intake despite extended abstinence from cocaine. These data demonstrate that cocaine leaves a long-lasting imprint on the dopamine system that is activated by re-exposure to cocaine. Further, these results provide a potential mechanism for severe cocaine binge episodes, which occur even after sustained abstinence from cocaine, and suggest that treatments aimed at transporter sites may be efficacious in promoting binge termination following relapse.
  
  
  
  Tolerance is a DSM-V criterion for substance abuse disorders. Abusers consistently show reduced subjective effects of cocaine concomitant with reduced effects of cocaine at its main site of action, the dopamine transporter (DAT). Preclinical literature has shown that reduced cocaine potency at the DAT increases cocaine taking, highlighting the key role of tolerance in addiction. Addiction is characterized by cycles of abstinence, often for many months, followed by relapse, making it important to determine possible interactions between abstinence and subsequent drug re-exposure. Using a rodent model of cocaine abuse, we found long-lasting, possibly permanent, cocaine-induced alterations to the DAT, whereby cocaine tolerance is reinstated by minimal drug exposure, even after recovery of DAT function over prolonged abstinence periods.
authors.affiliation: Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157.
authors.forename: Cody A
authors.identifier: 0000-0001-9871-2089
authors.initials: CA
authors.lastname: Siciliano
authors.affiliation: Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157.
authors.forename: Steve C
authors.identifier: 0000-0002-7093-6774
authors.initials: SC
authors.lastname: Fordahl
authors.affiliation: Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157 srjones@wakehealth.edu.
authors.forename: Sara R
authors.identifier: 0000-0002-3424-7576
authors.initials: SR
authors.lastname: Jones
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003042:Cocaine / Q000008:administration & dosage* / Q000506:poisoning*; D019970:Cocaine-Related Disorders / Q000503:physiopathology*; D050483:Dopamine Plasma Membrane Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance; D008124:Locomotion / Q000187:drug effects; D036881:Long-Term Synaptic Depression; D008297:Male; D009473:Neuronal Plasticity / Q000187:drug effects*; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012646:Self Administration
chemical_list: D050483:Dopamine Plasma Membrane Transport Proteins; D003042:Cocaine
keywords: abstinence; addiction; psychostimulant; relapse; tolerance; voltammetry