Does methylphenidate enhance cognition in normal rats and does it affect neuronal population?

Objective: Methylphenidate [MPH] is one of the drugs of choice for children with Attention Deficit Hyperactivity Disorder [ADHD] since many decades with good effect. Consumption of this drug by normal children and adolescents to boost their cognition skills is of concern. MPH induced cognitive enhancement involves brain dopamine and norepinephrine levels in areas concerned with cognition especially hippocampus. Altered expression of these neurotransmitters can affect neuronal population of hippocampus which may have the significant effect in later part of the life. Hence we evaluate the effect of MPH on cognition and histopathological changes in the hippocampus and dentate gyrus. Methods: Two month old male wistar rats were given either 2 or 5 mg/kg dose of MPH for 10 successive days and another set of rats served as control. The rats were tested for learning and memory activities followed by histopathological studies in hippocampus and dentate gyrus using Nissl staining. Results: MPH at both the doses has enhanced learning abilities as well as retention of memory. The histopathological studies did not show any significant effect on dentate gyrus as well as hippocampus. Conclusion: Though MPH is known to provide sound results in ADHD, from the present study it is clear that MPH treatment in normal rats also temporarily enhance the cognitive skills especially declarative memory. However, its effect on long term memory is to be investigated. MPH treatment has not affected the neuronal population hence possible cytotoxic effects on neurons can be ruled out from the present study.