title: Chronic Treatment with a Clinically Relevant Dose of Methylphenidate Increases Glutamate Levels in Cerebrospinal Fluid and Impairs Glutamatergic Homeostasis in Prefrontal Cortex of Juvenile Rats.
abstract: The understanding of the consequences of chronic treatment with methylphenidate is very important since this psychostimulant is extensively prescribed to preschool age children, and little is known about the mechanisms underlying the persistent changes in behavior and neuronal function related with the use of methylphenidate. In this study, we initially investigate the effect of early chronic treatment with methylphenidate on amino acids profile in cerebrospinal fluid and prefrontal cortex of juvenile rats, as well as on glutamatergic homeostasis, Na(+),K(+)-ATPase function, and balance redox in prefrontal cortex of rats. Wistar rats at early age received intraperitoneal injections of methylphenidate (2.0 mg/kg) or an equivalent volume of 0.9% saline solution (controls), once a day, from the 15th to the 45th day of age. Twenty-four hours after the last injection, the animals were decapitated and the cerebrospinal fluid and prefrontal cortex were obtained. Results showed that methylphenidate altered amino acid profile in cerebrospinal fluid, increasing the levels of glutamate. Glutamate uptake was decreased by methylphenidate administration, but GLAST and GLT-1 were not altered by this treatment. In addition, the astrocyte marker GFAP was not altered by MPH. The activity and immunocontent of catalytic subunits (α1, α2, and α3) of Na(+),K(+)-ATPase were decreased in prefrontal cortex of rats subjected to methylphenidate treatment, as well as changes in α1 and α2 gene expression of catalytic α subunits of Na(+),K(+)-ATPase were also observed. CAT activity was increased and SOD/CAT ratio and sulfhydryl content were decreased in rat prefrontal cortex. Taken together, our results suggest that chronic treatment with methylphenidate at early age induces excitotoxicity, at least in part, due to inhibition of glutamate uptake probably caused by disturbances in the Na(+),K(+)-ATPase function and/or in protein damage observed in the prefrontal cortex.
authors.affiliation: Laboratório de Neuroproteção e Doenças Metabólicas, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600-Anexo, CEP 90035-003, Porto Alegre, RS, Brazil.
authors.forename: Felipe
authors.initials: F
authors.lastname: Schmitz
authors.affiliation: Laboratório de Neuroproteção e Doenças Metabólicas, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600-Anexo, CEP 90035-003, Porto Alegre, RS, Brazil.
authors.forename: Paula
authors.initials: P
authors.lastname: Pierozan
authors.affiliation: Laboratório de Neuroproteção e Doenças Metabólicas, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600-Anexo, CEP 90035-003, Porto Alegre, RS, Brazil.
authors.forename: André F
authors.initials: AF
authors.lastname: Rodrigues
authors.affiliation: Laboratório de Neuroproteção e Doenças Metabólicas, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600-Anexo, CEP 90035-003, Porto Alegre, RS, Brazil.
authors.forename: Helena
authors.initials: H
authors.lastname: Biasibetti
authors.affiliation: Serviço de Genética Médica, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil.
authors.forename: Daniella M
authors.initials: DM
authors.lastname: Coelho
authors.affiliation: Laboratório de Sinalização Glutamatérgica, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Ben Hur
authors.initials: BH
authors.lastname: Mussulini
authors.affiliation: Laboratório de Sinalização Glutamatérgica, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Mery S L
authors.initials: MS
authors.lastname: Pereira
authors.affiliation: Laboratório de Biologia Molecular, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Mariana M
authors.initials: MM
authors.lastname: Parisi
authors.affiliation: Laboratório de Biologia Molecular, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Florencia
authors.initials: F
authors.lastname: Barbé-Tuana
authors.affiliation: Laboratório de Sinalização Glutamatérgica, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Diogo L
authors.initials: DL
authors.lastname: de Oliveira
authors.affiliation: Serviço de Genética Médica, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil.
authors.forename: Carmen R
authors.initials: CR
authors.lastname: Vargas
authors.affiliation: Laboratório de Neuroproteção e Doenças Metabólicas, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600-Anexo, CEP 90035-003, Porto Alegre, RS, Brazil. wyse@ufrgs.br.
authors.forename: Angela T S
authors.initials: AT
authors.lastname: Wyse
mesh_terms: D027322:Amino Acid Transport System X-AG / Q000378:metabolism; D000818:Animals; D034961:Antigens, Nuclear / Q000378:metabolism; D020134:Catalytic Domain; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D018698:Glutamic Acid / Q000134:cerebrospinal fluid*; D006706:Homeostasis / Q000187:drug effects*; D007150:Immunohistochemistry; D008297:Male; D008774:Methylphenidate / Q000494:pharmacology*; D008954:Models, Biological; D009419:Nerve Tissue Proteins / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D017397:Prefrontal Cortex / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D017208:Rats, Wistar; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism
chemical_list: D027322:Amino Acid Transport System X-AG; D034961:Antigens, Nuclear; D005904:Glial Fibrillary Acidic Protein; D009419:Nerve Tissue Proteins; C546339:Rbfox3 protein, rat; D008774:Methylphenidate; D018698:Glutamic Acid; D000254:Sodium-Potassium-Exchanging ATPase
keywords: Cerebrospinal fluid; Excitotoxicity glutamatergic; Juvenile rats; Methylphenidate; Prefrontal cortex; α subunits of Na+,K+-ATPase