title: Prolonged methylphenidate treatment alters the behavioral diurnal activity pattern of adult male Sprague-Dawley rats.
abstract: Methylphenidate (MPD) is becoming a drug of abuse among adult professionals and students, alike. Yet, few studies have investigated its long-term effects on the adult population. We hypothesized that prolonged administration of MPD leads to changes in the diurnal horizontal activity (HA) pattern, an effect persisting beyond acute drug effects. Four groups of adult male Sprague-Dawley rats (N=32) were divided into a saline/control, 0.6, 2.5, or 10.0 mg/kg MPD group. Each group was treated with saline on experimental day 1, followed by six consecutive days of designated treatment (days 2-7), then, after three consecutive days of washout (days 8-10), each group was re-challenged with its respective treatment (day 11). Activity was monitored continuously throughout the 11 experimental days. There was a dose-dependent increase in HA in the first hour post-injection. The 0.6 mg/kg MPD group exhibited changes in diurnal activity pattern only during the wash-out period. The 2.5 mg/kg MPD group exhibited the most profound changes in HA after 6 days of continuous injection, washout, and MPD re-challenge (p<0.05, p=0.001, p<0.001) respectively, and the 10.0 mg/kg MPD group exhibited changes during the washout and re-challenge periods (p<0.01, p<0.001), respectively. In conclusion, prolonged administration of MPD modulated the diurnal HA pattern in a dose-dependent manner.
authors.affiliation: Department of Neurobiology and Anatomy, The University of Texas-Medical School, Houston, Texas 77225, USA.
authors.forename: Mohamed F
authors.initials: MF
authors.lastname: Algahim
authors.forename: Pamela B
authors.initials: PB
authors.lastname: Yang
authors.forename: Victor T
authors.initials: VT
authors.lastname: Wilcox
authors.forename: Keith D
authors.initials: KD
authors.lastname: Burau
authors.forename: Alan C
authors.initials: AC
authors.lastname: Swann
authors.forename: Nachum
authors.initials: N
authors.lastname: Dafny
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D002940:Circadian Rhythm / Q000187:drug effects*; D003627:Data Interpretation, Statistical; D004305:Dose-Response Relationship, Drug; D008297:Male; D008774:Methylphenidate / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000697:Central Nervous System Stimulants; D008774:Methylphenidate