Related Experiment Video
Updated: Jun 20, 2026
A General Method for Evaluating Deep Brain Stimulation Effects on Intravenous Methamphetamine Self-Administration
Published on: January 22, 2016
The effects of chronic methylphenidate administration on operant test battery performance in juvenile rhesus monkeys
J S Rodriguez1, S M Morris, C E Hotchkiss
1Division of Neurotoxicology, National Center for Toxicological Research, FDA, Jefferson, AR, United States. rodriguezj13@uthscsa.edu
Insights
Methylphenidate (MPH) at lower doses did not impair juvenile rhesus monkeys' cognitive performance. Higher MPH doses (12.5 mg/kg) reduced motivation and task completion, suggesting potential side effects rather than cognitive deficits.
Area of Science:
- Neuroscience
- Behavioral Pharmacology
- Toxicology
Background:
- Methylphenidate (MPH) is a common ADHD treatment.
- Concerns exist regarding MPH's genotoxic potential in children.
- This study investigated chronic MPH effects on juvenile nonhuman primate behavior.
Purpose of the Study:
- To assess the impact of chronic methylphenidate (MPH) administration on cognitive functions in juvenile rhesus monkeys.
- To evaluate learning, motivation, and memory using operant behavioral tasks.
- To correlate MPH dosage with behavioral performance and potential cognitive impairments.
Main Methods:
- Juvenile male rhesus monkeys (n=10/group) received chronic oral MPH (0.15-12.5 mg/kg) for 66 weeks.
- Behavioral performance was assessed using the NCTR Operant Test Battery (OTB).
- Tasks included Incremental Repeated Acquisition, Progressive Ratio, Conditioned Position Responding, and Delayed Matching-to-Sample.
Main Results:
- MPH up to 2.5 mg/kg twice daily showed no performance difference compared to controls.
- A high dose of 12.5 mg/kg twice daily significantly decreased task completion and response rates.
- Performance decrements were attributed to reduced motivation, consistent with stimulant appetite suppression.
Conclusions:
- Chronic MPH administration at therapeutic doses appears well-tolerated in juvenile rhesus monkeys.
- High-dose MPH can reduce motivation and task performance, likely due to appetite suppression.
- Current findings do not strongly indicate MPH-induced cognitive impairment in this model.
Abstract:
Methylphenidate (MPH) is an amphetamine derivative widely prescribed for the treatment of attention deficit-hyperactivity disorder. Recent concern over its genotoxic potential in children [11] spurred a study on the effects of chronic MPH treatment in a nonhuman primate population and the studies reported here were conducted in conjunction with that study in the same animals. Here, the focus was on the ability of juvenile rhesus monkeys to learn how to perform a battery of operant behavioral tasks while being treated chronically with MPH. Performance of the National Center for Toxicological Research (NCTR) Operant Test Battery (OTB) was used to quantify the learning of tasks thought to model specific aspects of cognitive function including learning, motivation, color and position discrimination, and short-term memory. The OTB tasks designed to assess these specific behaviors included Incremental Repeated Acquisition (IRA), Progressive Ratio (PR), Conditioned Position Responding (CPR), and Delayed Matching-to-Sample (DMTS), respectively. Juvenile males (n=10/group) pressed levers and press-plates for banana-flavored food pellets. Subjects were treated orally, twice a day, five days per week (M-F) for 66 weeks with escalating doses (0.15 mg/kg initially, increased to 2.5 mg/kg for the low dose group and to 12.5 mg/kg for the high dose group) and tested in OTB tasks 30 to 60 min after the morning dose. The findings indicate that MPH at doses up to 2.5 mg/kg twice per day were well tolerated (performance was no different than controls) but at doses of 12.5 mg/kg twice per day there was a significant decrement in OTB performance, characterized by decreases in both percent task completed and response rates for all tasks. These effects of MPH seem primarily due to decreases in motivation to perform for food, which is not surprising given the well known appetite suppressing effects of amphetamine-like stimulants. Thus, the current data do not strongly suggest cognitive impairments following chronic MPH administration.
