The multifaceted effects of oral administration of methylphenidate in juvenile rats: anxiety, activity, and attention.

In previous studies, acutely administered oral methylphenidate (MPD, 3mg/kg) prior to testing improved performance on the radial arm maze in juvenile rats. In order to examine the mechanisms producing this improvement we administered MPD once prior to each test of anxiety, locomotor activity and attention. On postnatal day (PND) 22 on an elevated plus maze, rats spent more time beyond the rails on the open arms and showed altered risk-assessment behaviors suggesting an anxiolytic-like effect of MPD. Grid crossings on the plus maze indicated that MPD increased locomotor activity, as did activity recording on PND 23. In another group of juveniles, MPD improved performance in a multi-trial attention task in an age-dependent fashion. These data suggest that oral MPD has multifaceted effects on juvenile rats that together improve performance on cognitive tests such as the radial arm maze. In addition, our data support human studies finding multifaceted effects of MPD.