TITLE:
Adolescent and Adult Circadian Rhythm Activity Modulated Differently Following Chronic Methylphenidate Administration
AUTHORS:
Simon Kayyal, Tan Trinh, Nachum Dafny
KEYWORDS:
Circadian Rhythm, Adolescent, Adult
JOURNAL NAME:
Journal of Behavioral and Brain Science,
Vol.5 No.2,
February
26,
2015
ABSTRACT: Methylphenidate is one of the most common pharmaceutical treatments for Attention Deficit Hyperactive Disorder (ADHD). It is also gaining popularity as a cognitive enhancement and recreational substance. The current study assesses the long-term effects of methylphenidate (MPD) on the circadian rhythm activity pattern of adolescent and adult male Sprague-Dawley (SD) rats. The experiment lasted for 11 days of non-stop recording, the evaluation was divided into 4 phases: acute, induction, washout, and expression phases. Circadian rhythm changes in each phase were compared between the adolescent and adult rats using the following parameters MESOR (midline estimating statistic of rhythm) or average activity, amplitude (distance from MESOR to the peak activity), and acrophase (time at which peak amplitude occurs). Overall, more significant changes in circadian rhythm pattern among adult rats were observed as compared to adolescent rats. As the circadian rhythm governs the diurnal locomotor activity pattern, changes in the locomotor pattern induced by chronic treatment MPD indicate that the drug exerts a long-term effect on the circadian rhythm.