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Exposure to methylphenidate during infancy and adolescence in non-human animals and sensitization to abuse of psychostimulants later in life: a systematic review.

INTRODUCTION
Attention deficit hyperactivity disorder (ADHD) is a neuropsychiatric pathology that has an important prevalence among young people and is difficult to diagnose. It is usually treated with methylphenidate, a psychostimulant with a mechanism of action similar to that of cocaine. Previous studies show that repeated use of psychostimulants during childhood or adolescence may sensitize subjects, making them more prone to later abuse of psychostimulant drugs such as cocaine and methamphetamine.


OBJECTIVE
To review experimental studies in non-human models (rodents and monkeys) treated with methylphenidate during infancy or adolescence and tested for reinforcing effects on psychostimulant drugs in adulthood.


METHOD
Systematic collection of data was performed on four databases (Web of Knowledge, PsycARTICLE, PubMed and SciELO). The initial search identified 202 articles published from 2009 to 2014, which were screened for eligibility. Seven articles met the inclusion criteria and were reviewed in this study.


RESULTS
The findings indicate that early exposure to methylphenidate has an effect on an ADHD animal model, specifically, on spontaneously hypertensive strain rats, especially those tested using the self-administration paradigm.


CONCLUSION
Future studies should prioritize the spontaneously hypertensive rat strain - an animal model of ADHD. Experimental designs comparing different behavioral paradigms and modes of administration using this strain could lead to improved understanding of the effects of exposure to methylphenidate during childhood and adolescence.