title: Evaluation of light/dark cycle in anxiety- and depressive-like behaviors after regular treatment with methylphenidate hydrochloride in rats of different ages.
abstract: OBJECTIVE
  Methylphenidate hydrochloride is the most widely used medication for treatment and management of attention-deficit hyperactivity disorder. However, the chronic effects of methylphenidate hydrochloride on anxiety- and depressive-like rat behaviors remain poorly investigated. In this context, the present study evaluated the effects of treatment with methylphenidate hydrochloride on anxiety- and depressive-like behaviors using young and adult rats during the light and the dark cycle.
  
  
  METHODS
  Male Wistar rats (25 or 60 days old) received a once-daily (in either the light or dark cycle) methylphenidate hydrochloride (2mg/kg) or saline intraperitoneal injection for 28 days. We performed elevated plus maze and forced swimming test two hours after the last injection.
  
  
  RESULTS
  The light/dark cycle was a significant factor in the anxiety-like behaviors; however, no significant interaction between all three factors (cycle, age and methylphenidate hydrochloride) was found. Nevertheless, we observed a nominally significant interaction between the light/ dark cycle and age in the forced swimming test.
  
  
  CONCLUSIONS
  Our results have shown that age and the light/dark cycle are more significant modulators of anxiety- and depressive-like behaviors than methylphenidate hydrochloride treatment.
authors.affiliation: Universidade do Extremo Sul Catarinense, Criciúma, SC, Brazil.
authors.forename: Karin M
authors.initials: KM
authors.lastname: Gomes
authors.forename: Renan P
authors.initials: RP
authors.lastname: Souza
authors.forename: Cecília G
authors.initials: CG
authors.lastname: Inácio
authors.forename: Samira S
authors.initials: SS
authors.lastname: Valvassori
authors.forename: Gislaine Z
authors.initials: GZ
authors.lastname: Réus
authors.forename: Márcio R
authors.initials: MR
authors.lastname: Martins
authors.forename: Clarissa M
authors.initials: CM
authors.lastname: Comim
authors.forename: João
authors.initials: J
authors.lastname: Quevedo
mesh_terms: D000367:Age Factors; D000818:Animals; D014151:Anti-Anxiety Agents / Q000627:therapeutic use*; D000928:Antidepressive Agents / Q000627:therapeutic use*; D001008:Anxiety Disorders / Q000188:drug therapy* / Q000523:psychology; D001289:Attention Deficit Disorder with Hyperactivity / Q000188:drug therapy; D003866:Depressive Disorder / Q000188:drug therapy* / Q000523:psychology; D008297:Male; D008774:Methylphenidate / Q000627:therapeutic use*; D017440:Photoperiod; D051381:Rats; D017208:Rats, Wistar
chemical_list: D014151:Anti-Anxiety Agents; D000928:Antidepressive Agents; D008774:Methylphenidate