title: Transcranial direct current stimulation improves short-term memory in an animal model of attention-deficit/hyperactivity disorder.
abstract: Attention deficit hyperactivity disorder (ADHD) is characterized by impairing levels of hyperactivity, impulsivity and inattention. However, different meta-analyses have reported disruptions in short and long-term memory in ADHD patients. Previous studies indicate that mnemonic dysfunctions might be the result of deficits in attentional circuits, probably due to ineffective dopaminergic modulation of hippocampal synaptic plasticity. In this study we aimed to evaluate the potential therapeutic effects of a neuromodulatory technique, transcranial direct current stimulation (tDCS), in short-term memory (STM) deficits presented by the spontaneous hypertensive rats (SHR), the most widely used animal model of ADHD. Adult male SHR and Wistar Kyoto rats (WKY) were subjected to a constant electrical current of 0.5 mA intensity applied on the frontal cortex for 20 min/day during 8 days. STM was evaluated with an object recognition test conducted in an open field. Exploration time and locomotion were recorded, and brain regions were dissected to determine dopamine and BDNF levels. SHR spent less time exploring the new object when compared to WKY, and tDCS improved object recognition deficits in SHR without affecting WKY performance. Locomotor activity was higher in SHR and it was not affected by tDCS. After stimulation, dopamine levels were increased in the hippocampus and striatum of both strains, while BDNF levels were increased only in the striatum of WKY. These findings suggest that tDCS on the frontal cortex might be able to improve STM deficits present in SHR, which is potentially related to dopaminergic neurotransmission in the hippocampus and striatum of those animals.
authors.affiliation: Post-Graduate Program in Medicine: Medical Sciences, School of Medicine, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; Animal Experimentation Unit and Graduate Research Group, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS 90035-003, Brazil; Biochemistry Department, Institute of Basic Health Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; Laboratory of Pain Pharmacology and Neuromodulation: Pre clinical studies-Pharmacology Department, Institute of Basic Health Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Douglas Teixeira
authors.initials: DT
authors.lastname: Leffa
authors.affiliation: Animal Experimentation Unit and Graduate Research Group, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS 90035-003, Brazil; Laboratory of Pain Pharmacology and Neuromodulation: Pre clinical studies-Pharmacology Department, Institute of Basic Health Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Andressa
authors.initials: A
authors.lastname: de Souza
authors.affiliation: Post-Graduate Program in Medicine: Medical Sciences, School of Medicine, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; Animal Experimentation Unit and Graduate Research Group, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS 90035-003, Brazil; Laboratory of Pain Pharmacology and Neuromodulation: Pre clinical studies-Pharmacology Department, Institute of Basic Health Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Vanessa Leal
authors.initials: VL
authors.lastname: Scarabelot
authors.affiliation: Post-Graduate Program in Medicine: Medical Sciences, School of Medicine, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; Animal Experimentation Unit and Graduate Research Group, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS 90035-003, Brazil; Laboratory of Pain Pharmacology and Neuromodulation: Pre clinical studies-Pharmacology Department, Institute of Basic Health Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Liciane Fernandes
authors.initials: LF
authors.lastname: Medeiros
authors.affiliation: Post-Graduate Program in Medicine: Medical Sciences, School of Medicine, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; Animal Experimentation Unit and Graduate Research Group, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS 90035-003, Brazil; Laboratory of Pain Pharmacology and Neuromodulation: Pre clinical studies-Pharmacology Department, Institute of Basic Health Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Carla
authors.initials: C
authors.lastname: de Oliveira
authors.affiliation: Department of Psychiatry, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; ADHD Outpatient Program, Hospital de Clínicas de Porto Alegre, Brazil.
authors.forename: Eugenio Horacio
authors.initials: EH
authors.lastname: Grevet
authors.affiliation: Post-Graduate Program in Medicine: Medical Sciences, School of Medicine, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Wolnei
authors.initials: W
authors.lastname: Caumo
authors.affiliation: Biochemistry Department, Institute of Basic Health Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Diogo Onofre
authors.initials: DO
authors.lastname: de Souza
authors.affiliation: Department of Psychiatry, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; ADHD Outpatient Program, Hospital de Clínicas de Porto Alegre, Brazil; National Institute of Developmental Psychiatry for Children and Adolescents, Brazil.
authors.forename: Luis Augusto Paim
authors.initials: LAP
authors.lastname: Rohde
authors.affiliation: Post-Graduate Program in Medicine: Medical Sciences, School of Medicine, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; Animal Experimentation Unit and Graduate Research Group, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS 90035-003, Brazil; Laboratory of Pain Pharmacology and Neuromodulation: Pre clinical studies-Pharmacology Department, Institute of Basic Health Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil. Electronic address: iracitorres@gmail.com.
authors.forename: Iraci L S
authors.initials: ILS
authors.lastname: Torres
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001289:Attention Deficit Disorder with Hyperactivity / Q000150:complications* / Q000473:pathology; D001921:Brain / Q000378:metabolism; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism; D004195:Disease Models, Animal; D004298:Dopamine / Q000378:metabolism; D008124:Locomotion / Q000502:physiology; D008297:Male; D008569:Memory Disorders / Q000209:etiology* / Q000628:therapy*; D008570:Memory, Short-Term / Q000502:physiology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D021641:Recognition, Psychology / Q000502:physiology; D013223:Statistics as Topic; D065908:Transcranial Direct Current Stimulation
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D004298:Dopamine
keywords: ADHD; Dopamine; Memory; SHR; tDCS