title: Cognitive improvement by acute growth hormone is mediated by NMDA and AMPA receptors and MEK pathway.
abstract: It has been reported that Growth hormone (GH) has an immediate effect enhancing excitatory postsynaptic potentials mediated by AMPA and NMDA receptors in hippocampal area CA1. As GH plays a role in adult memory processing, this work aims to study the acute effects of GH on working memory tasks in rodents and the possible involvement of NMDA and AMPA receptors and also the MEK/ERK signalling pathway. To evaluate memory processes, two different tests were used, the spatial working memory 8-arm radial maze, and the novel object recognition as a form of non-spatial working memory test. Acute GH treatment (1mg/kg i.p., 1h) improved spatial learning in the radial maze respect to the control group either in young rats (reduction of 46% in the performance trial time and 61% in the number of errors), old rats (reduction of 38% in trial time and 48% in the number of errors), and adult mice (reduction of 32% in the performance time and 34% in the number of errors). GH treatment also increased the time spent exploring the novel object respect to the familiar object compared to the control group in young rats (from 63% to 79%), old rats (from 53% to 70%), and adult mice (from 61 to 68%). The improving effects of GH on working memory tests were blocked by the NMDA antagonist MK801 dizocilpine (0.025 mg/kg i.p.) injected 10 min before the administration of GH, in both young and old rats. In addition, the AMPA antagonist DNQX (1mg/kg i.p.) injected 10 min before the administration of GH to young rats, blocked the positive effect of GH. Moreover, in mice, the MEK inhibitor SL 327 (20mg/kg i.p.) injected 30 min before the administration of GH, blocked the positive effect of GH on radial maze and the novel object recognition. In conclusion, GH improved working memory processes through both glutamatergic receptors NMDA and AMPA and it required the activation of extracellular MEK/ERK signalling pathway. These effects could be related to the enhancement of excitatory synaptic transmission in the hippocampus reported by GH.
authors.affiliation: Laboratorio de Neurofisiología, Departamento de Biología, Universitat de les Illes Balears, Cra. Valldemossa km 7.5, E-07122 Palma de Mallorca, Spain. margaramis87@hotmail.com
authors.forename: Margarita
authors.initials: M
authors.lastname: Ramis
authors.forename: Fiorella
authors.initials: F
authors.lastname: Sarubbo
authors.forename: Jessica
authors.initials: J
authors.lastname: Sola
authors.forename: Sara
authors.initials: S
authors.lastname: Aparicio
authors.forename: Celia
authors.initials: C
authors.lastname: Garau
authors.forename: Antonio
authors.initials: A
authors.lastname: Miralles
authors.forename: Susana
authors.initials: S
authors.lastname: Esteban
mesh_terms: D000367:Age Factors; D000607:Aminoacetonitrile / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004347:Drug Interactions; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D013006:Growth Hormone / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D008297:Male; D008570:Memory, Short-Term / Q000187:drug effects* / Q000502:physiology*; D051379:Mice; D011480:Protease Inhibitors / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D018691:Excitatory Amino Acid Antagonists; D011480:Protease Inhibitors; D011810:Quinoxalines; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; C424127:SL 327; D000607:Aminoacetonitrile; C056723:FG 9041; D016291:Dizocilpine Maleate; D013006:Growth Hormone
keywords: 6,7-dinitroquinoxaline-2,3-dione; AMPA; DNQX; ERK; GABA(A); GH; Growth hormone; MAPK; MAPK/ERK kinase; MEK; MK801; N-methyl-d-aspartate; NMDA; Object recognition; Radial maze; SL 327; WM; dizocilpine; extracellular signal-regulated kinase; growth hormone; mitogen activated protein kinase; working memory; α-amino-(4-aminophenyl-thio)-methylene-2-(trifluoromethyl)-benzene-acetonitrile; α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid; γ-aminobutyric acid type A