title: Cross-sensitization of the reinforcing effects of cocaine and amphetamine in rats.
abstract: BACKGROUND
  Cross-sensitization between cocaine and amphetamine has been demonstrated in different behavioral paradigms. There is a relative paucity of studies examining whether cross-sensitization occurs between amphetamine and cocaine when both are self-administered.
  
  
  OBJECTIVE
  The current study was designed to test whether animals sensitized to the reinforcing effects of cocaine would show cross-sensitization of the reinforcing effects of amphetamine, using a self-administration paradigm.
  
  
  METHODS
  Male, Sprague-Dawley rats were trained to self-administer cocaine and given limited or high exposure to cocaine under a fixed ratio (FR) 1 procedure. After the initial exposure to cocaine, animals self-administered cocaine (1.5 mg/kg per injection) under a progressive ratio (PR) procedure. Subsequently, breakpoints on a PR schedule and rates of intake on an FR schedule maintained by different doses of amphetamine were assessed.
  
  
  RESULTS
  Animals with high initial exposure to cocaine (40 injections of 1.5 mg/kg per injection per day for 5 days) showed stable breakpoints throughout testing. Animals given limited initial cocaine exposure (20 injections of 0.75 mg/kg per injection for 1 day) produced a gradual increase in breakpoints maintained by cocaine over time (i.e., sensitization of the reinforcing effects of cocaine). When subsequently tested with amphetamine, the dose-effect curve was shifted upward in the limited-exposure group relative to the high-exposure group, suggesting cross-sensitization of the reinforcing effects of amphetamine.
  
  
  CONCLUSIONS
  Sensitization of the reinforcing effects of cocaine resulted in cross-sensitization of the reinforcing effects of amphetamine. This phenomenon occurs even when both drugs are self-administered.
authors: Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Medical Center Blvd., Winston-Salem, NC 27157, USA.
authors: Yu
authors: Y
authors: Liu
authors: Drake
authors: D
authors: Morgan
authors: David C S
authors: DC
authors: Roberts
mesh_terms: D000661:Amphetamine / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D000697:Central Nervous System Stimulants / Q000008:administration & dosage / Q000494:pharmacology*; D003042:Cocaine / Q000008:administration & dosage / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects; D018765:Dopamine Uptake Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology; D012646:Self Administration
chemical_list: D000697:Central Nervous System Stimulants; D018765:Dopamine Uptake Inhibitors; D000661:Amphetamine; D003042:Cocaine
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