title: The effect of methylphenidate and rearing environment on behavioral inhibition in adult male rats.
abstract: BACKGROUND
  The ability to withhold reinforced responses-behavioral inhibition-is impaired in various psychiatric conditions including Attention Deficit Hyperactivity Disorder (ADHD). Methodological and analytical limitations have constrained our understanding of the effects of pharmacological and environmental factors on behavioral inhibition.
  
  
  OBJECTIVE
  To determine the effects of acute methylphenidate (MPH) administration and rearing conditions (isolated vs. pair-housed) on behavioral inhibition in adult rats.
  
  
  METHODS
  Inhibitory capacity was evaluated using two response-withholding tasks, differential reinforcement of low rates (DRL) and fixed minimum interval (FMI) schedules of reinforcement. Both tasks made sugar pellets contingent on intervals longer than 6 s between consecutive responses. Inferences on inhibitory and timing capacities were drawn from the distribution of withholding times (interresponse times, or IRTs).
  
  
  RESULTS
  MPH increased the number of intervals produced in both tasks. Estimates of behavioral inhibition increased with MPH dose in FMI and with social isolation in DRL. Nonetheless, burst responding in DRL and the divergence of DRL data relative to past studies, among other limitations, undermined the reliability of DRL data as the basis for inferences on behavioral inhibition.
  
  
  CONCLUSIONS
  Inhibitory capacity was more precisely estimated from FMI than from DRL performance. Based on FMI data, MPH, but not a socially enriched environment, appears to improve inhibitory capacity. The highest dose of MPH tested, 8 mg/kg, did not reduce inhibitory capacity but reduced the responsiveness to waiting contingencies. These results support the use of the FMI schedule, complemented with appropriate analytic techniques, for the assessment of behavioral inhibition in animal models.
authors: Arizona State University, Tempe, AZ, USA.
authors: Jade C
authors: JC
authors: Hill
authors: Pablo
authors: P
authors: Covarrubias
authors: Joel
authors: J
authors: Terry
authors: Federico
authors: F
authors: Sanabria
mesh_terms: D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D006799:Housing, Animal; D007266:Inhibition, Psychological; D008297:Male; D008774:Methylphenidate / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012055:Reinforcement Schedule; D012934:Social Isolation
chemical_list: D008774:Methylphenidate