Reinforcing effects of methylphenidate: influence of dose and behavioral demands following drug administration.
BACKGROUND
The reinforcing effects of stimulant drugs such as D-amphetamine, caffeine, and cocaine are modulated by behavioral demands following drug administration.


OBJECTIVE
The objective of this study was to assess the reinforcing effects of methylphenidate under different behavioral demands using a modified progressive-ratio procedure.


METHODS
The reinforcing effects of oral methylphenidate (0, 10, 20, and 40 mg) were assessed in seven healthy adult volunteers under both performance and relaxation conditions. Performance sessions required volunteers to complete simple arithmetic problems for three 50-min blocks. Relaxation sessions required volunteers to sit quietly in a semi-reclined position in a darkened room for three 50-min blocks. Two sampling sessions (one performance and one relaxation session) always preceded two self-administration sessions (one performance and one relaxation session) and the order of relaxation and performance sessions was constant within a dose condition.


RESULTS
Methylphenidate significantly increased break point and number of capsules earned on the modified progressive-ratio procedure as an increasing function of dose under the performance, but not the relaxation, condition. Methylphenidate produced comparable stimulant-like subject ratings under both the performance and relaxation conditions.


CONCLUSIONS
The findings of the present experiment suggest that the reinforcing effects of methylphenidate, like D-amphetamine and cocaine, are influenced by behavioral demands following drug administration.
Stoops
William W
WW
Department of Psychology, University of Kentucky, Lexington, KY 40536-0086, USA.
Lile
Joshua A
JA
Fillmore
Mark T
MT
Glaser
Paul E A
PE
Rush
Craig R
CR
D000284:Administration, Oral; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002214:Capsules; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007406:Interview, Psychological / Q000379:methods; D008297:Male; D008433:Mathematics; D008774:Methylphenidate / Q000008:administration & dosage / Q000493:pharmacokinetics*; D018579:Patient Selection; D011340:Problem Solving / Q000187:drug effects / Q000502:physiology; D011597:Psychomotor Performance / Q000187:drug effects*; D012055:Reinforcement Schedule; D012064:Relaxation Therapy; D012646:Self Administration; D011795:Surveys and Questionnaires
D002214:Capsules; D008774:Methylphenidate