title: Changes in psychomotor effects of L-dopa and methylphenidate after sustained dopaminergic therapy in Parkinson's disease.
abstract: BACKGROUND
  Sustained drug therapy in Parkinson's disease may alter the psychomotor responses to acute challenges with dopaminergic drugs, L-dopa and methylphenidate, and cause cross sensitisation.
  
  
  METHODS
  The mood, psychomotor and reward potentiating effects of an acute challenge with L-dopa and methylphenidate on separate occasions were assessed under double blind (medication naïve) conditions after a placebo and then the testing sessions were repeated in the same (medication experienced) patients following a median period of 16.7 months of continuous dopaminergic drug therapy.
  
  
  RESULTS
  In the medication naïve condition, affect was not changed by L-dopa or methylphenidate and only L-dopa improved motor function. In the medication experienced condition, active drugs improved positive affect compared with the medication naïve condition and there was an enhanced effect of L-dopa on motor function. Reward responsivity was enhanced by both L-dopa and methylphenidate in medication naïve and experienced conditions.
  
  
  CONCLUSIONS
  Sustained dopaminergic drug therapy augments the motor effects of an acute challenge with L-dopa and induces euphoriant effects to L-dopa and methylphenidate challenges.
authors.affiliation: Department of Neurology, The Royal Melbourne Hospital, Victoria, Australia.
authors.forename: A H
authors.initials: AH
authors.lastname: Evans
authors.forename: A D
authors.initials: AD
authors.lastname: Lawrence
authors.forename: A J
authors.initials: AJ
authors.lastname: Lees
mesh_terms: D000328:Adult; D000339:Affect / Q000187:drug effects*; D000368:Aged; D000978:Antiparkinson Agents / Q000627:therapeutic use*; D000697:Central Nervous System Stimulants / Q000627:therapeutic use*; D015259:Dopamine Agents / Q000627:therapeutic use*; D004311:Double-Blind Method; D004359:Drug Therapy, Combination; D005059:Euphoria / Q000187:drug effects; D005260:Female; D006801:Humans; D007980:Levodopa / Q000627:therapeutic use*; D008134:Long-Term Care; D008297:Male; D008774:Methylphenidate / Q000627:therapeutic use*; D008875:Middle Aged; D009042:Motivation; D009460:Neurologic Examination / Q000187:drug effects; D010147:Pain Measurement; D010300:Parkinson Disease / Q000188:drug therapy*; D011597:Psychomotor Performance / Q000187:drug effects*; D012201:Reward
chemical_list: D000978:Antiparkinson Agents; D000697:Central Nervous System Stimulants; D015259:Dopamine Agents; D008774:Methylphenidate; D007980:Levodopa