title: Diurnal differences in memory and learning in young and adult rats treated with methylphenidate.
abstract: Methylphenidate (MPH) is a very effective treatment option for children and adolescents with attention-deficit/hyperactivity disorder. Nevertheless, there have been inconsistent reports regarding the effects of MPH on learning and memory. The aim of this study was to evaluate whether the treatment with MPH during the morning differs from that during the night on learning and memory (short and long term) in young and adult male Wistar rats. The animals received once daily intraperitoneal injection of either MPH (2 mg/kg) or saline (0.9%) for 28 days (either in the morning or at night). The animals underwent two behavioral tasks to evaluate learning and memory: inhibitory avoidance task and continuous multiple trials step-down inhibitory avoidance (CMIA). Young rats treated in the morning showed significant impaired long-term memory for inhibitory avoidance training and facilitated acquisition in the CMIA. Adult rats treated in the night showed impaired long-term retention in the CMIA. We observed similar performances in both tests for young rats treated at night or adult rats treated in the morning. Our results suggest that age and time of treatment can alter the MPH effects in learning and memory.
authors.affiliation: Laboratory of Neuroscience, National Institute of Translational Science and Technology in Medicine, Unidade Acadêmica de Ciências da Saúde, Universidade do Extremo Sul Catarinense, 88806-000 Criciúma, SC, Brazil.
authors.forename: Karin M
authors.initials: KM
authors.lastname: Gomes
authors.forename: Clarissa M
authors.initials: CM
authors.lastname: Comim
authors.forename: Samira S
authors.initials: SS
authors.lastname: Valvassori
authors.forename: Gislaine Z
authors.initials: GZ
authors.lastname: Réus
authors.forename: Cecília G
authors.initials: CG
authors.lastname: Inácio
authors.forename: Márcio R
authors.initials: MR
authors.lastname: Martins
authors.forename: Renan P
authors.initials: RP
authors.lastname: Souza
authors.forename: João
authors.initials: J
authors.lastname: Quevedo
mesh_terms: D000375:Aging; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects* / Q000502:physiology; D007274:Injections, Intraperitoneal; D008297:Male; D008568:Memory / Q000187:drug effects* / Q000502:physiology; D008570:Memory, Short-Term / Q000187:drug effects / Q000502:physiology; D008774:Methylphenidate / Q000008:administration & dosage*; D009483:Neuropsychological Tests; D018697:Nootropic Agents / Q000008:administration & dosage*; D017440:Photoperiod; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: D018697:Nootropic Agents; D008774:Methylphenidate