Does methylphenidate administration to juvenile rats cause altered and addictive behavior in adulthood?

Methylphenidate (MPH) is commonly prescribed drug for attention deficit hyperactivity disorder (ADHD) in children and these symptoms known to persist during adolescence and adulthood. The neural consequences like emotionality, anxiety like behavior and even addictive behavior in adolescence and adulthood after early-life exposure to MPH is not adequately addressed. Hence this study was designed to test whether MPH administration to juvenile rats cause altered and addictive behaviour in adulthood. Twenty three day old male rats were given either 2 or 5mg/kg dose of MPH for 22 consecutive days and another group of rats received saline. Four weeks after cessation of treatment rats were subjected to open field and dark/bright arena test to evaluate emotionality and anxiety like behavior and two choice ethanol tests for addictive behavior. Further rats were sacrificed and histomorphological studies of prefrontal cortex were performed. The present study demonstrates an increased emotional activity and anxiety like behavior which is associated with addictive behavior in rats during early adulthood after juvenile MPH treatment. A considerable neuronal loss was also observed in prefrontal cortex. MPH is been extensively and inappropriately used children with ADHD and the addictive behavior observed in the present study are of concern. Studies further directed towards addictive behavior and anatomical regions involved are warranted.