title: The effects of resistance exercise on cocaine self-administration, muscle hypertrophy, and BDNF expression in the nucleus accumbens.
abstract: Exercise is associated with positive outcomes in drug abusing populations and reduces drug self-administration in laboratory animals. To date, most research has focused on aerobic exercise, and other types of exercise have not been examined. This study examined the effects of resistance exercise (strength training) on cocaine self-administration and BDNF expression, a marker of neuronal activation regulated by aerobic exercise.
  
  
  
  Female rats were assigned to either exercising or sedentary conditions. Exercising rats climbed a ladder wearing a weighted vest and trained six days/week. Training consisted of a three-set "pyramid" in which the number of repetitions and resistance varied across three sets: eight climbs carrying 70% body weight (BW), six climbs carrying 85% BW, and four climbs carrying 100% BW. Rats were implanted with intravenous catheters and cocaine self-administration was examined. Behavioral economic measures of demand intensity and demand elasticity were derived from the behavioral data. BDNF mRNA expression was measured via qRT-PCR in the nucleus accumbens following behavioral testing.
  
  
  
  Exercising rats self-administered significantly less cocaine than sedentary rats. A behavioral economic analysis revealed that exercise increased demand elasticity for cocaine, reducing consumption at higher unit prices. Exercising rats had lower BDNF expression in the nucleus accumbens core than sedentary rats.
  
  
  
  These data indicate that resistance exercise decreases cocaine self-administration and reduces BDNF expression in the nucleus accumbens after a history of cocaine exposure. Collectively, these findings suggest that strength training reduces the positive reinforcing effects of cocaine and may decrease cocaine use in human populations.
authors.affiliation: Department of Psychology, University of Kentucky, Lexington, KY, United States.
authors.forename: Justin C
authors.initials: JC
authors.lastname: Strickland
authors.affiliation: Department of Psychiatry and Neurobehavioral Sciences, University of Virginia, Charlottesville, VA, United States.
authors.forename: Jean M
authors.initials: JM
authors.lastname: Abel
authors.affiliation: Department of Psychology, Franklin and Marshall College, Lancaster, PA, United States.
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Lacy
authors.affiliation: Department of Psychology, University of Kentucky, Lexington, KY, United States.
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Beckmann
authors.affiliation: Department of Psychology, Davidson College, Davidson, NC, United States.
authors.forename: Maryam A
authors.initials: MA
authors.lastname: Witte
authors.affiliation: Department of Psychiatry and Neurobehavioral Sciences, University of Virginia, Charlottesville, VA, United States.
authors.forename: Wendy J
authors.initials: WJ
authors.lastname: Lynch
authors.affiliation: Department of Psychology, Davidson College, Davidson, NC, United States; Program in Neuroscience, Davidson College, Davidson, NC, United States. Electronic address: masmith@davidson.edu.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Smith
mesh_terms: D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000096:biosynthesis* / Q000235:genetics; D003042:Cocaine / Q000008:administration & dosage*; D019970:Cocaine-Related Disorders / Q000235:genetics / Q000378:metabolism / Q000628:therapy; D005260:Female; D015870:Gene Expression; D006984:Hypertrophy; D053580:Muscle Strength / Q000502:physiology*; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism*; D010805:Physical Conditioning, Animal / Q000379:methods / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D012054:Reinforcement, Psychology; D055070:Resistance Training / Q000379:methods*; D012646:Self Administration
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D003042:Cocaine
keywords: Demand curve; Drug; Physical activity; Rat; Strength training