title: The stereotypy-inducing effects of N-substituted benztropine analogs alone and in combination with cocaine do not account for their blockade of cocaine self-administration.
abstract: BACKGROUND
  Previous studies have demonstrated that several N-substituted 4', 4″-diF-benztropine (BZT) analogs with high dopamine transporter affinity selectively decreased cocaine self-administration without affecting food-maintained behavior in rats.
  
  
  OBJECTIVE
  The present study examined if the decreases in cocaine self-administration are due to competition from excess behavioral activity (hyperlocomotion or stereotypy) induced by the BZT analogs alone or in combination with cocaine.
  
  
  RESULTS
  Pretreatments with the typical dopamine uptake inhibitor methylphenidate [1.0, 3.2, and 10 mg/kg, intraperitoneally (i.p.)] dose-dependently shifted the cocaine self-administration dose-effect curve (0, 0.032, 0.1, 0.32, and 1.0 mg/kg/injection) leftward. The shift in the dose-effect curve was obtained at doses of methylphenidate that, when administered alone, also decreased food-maintained behavior and increased locomotor activity and stereotypy. In contrast, the N-substituted BZT analogs, JHW 007 (1.0, 3.2, and 10 mg/kg, i.p.), AHN 1-055 (10 mg/kg), and, AHN 2-005 (10 mg/kg), as previously reported, decreased the maximum for the cocaine self-administration dose-effect curve, and did so at doses that were virtually without effects on food-maintained behavior. Further, the BZT analogs alone had minimal effects on locomotor activity and stereotypies and did not appreciably change the effects of cocaine on these measures when administered in combination with cocaine.
  
  
  CONCLUSIONS
  The present results suggest that the decrease in cocaine self-administration produced by the N-substituted BZT analogs is due to an antagonism of the reinforcing effects of cocaine rather than due to interference from competing behavioral overstimulation, and further supports the development of N-substituted BZT analogs as medications to treat cocaine abuse.
authors.affiliation: Psychobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, 251 Bayview Blvd, Baltimore, MD 21224, USA.
authors.forename: Libin
authors.initials: L
authors.lastname: Li
authors.forename: Takato
authors.initials: T
authors.lastname: Hiranita
authors.forename: Shuichiro
authors.initials: S
authors.lastname: Hayashi
authors.forename: Amy H
authors.initials: AH
authors.lastname: Newman
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Katz
mesh_terms: D000818:Animals; D001590:Benztropine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology*; D003042:Cocaine / Q000008:administration & dosage / Q000494:pharmacology*; D019970:Cocaine-Related Disorders / Q000517:prevention & control* / Q000523:psychology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005502:Food; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012054:Reinforcement, Psychology; D012646:Self Administration; D013239:Stereotyped Behavior / Q000187:drug effects*
chemical_list: D001590:Benztropine; D003042:Cocaine