Intracerebroventricular administration of ouabain, a Na/K-ATPase inhibitor, activates mTOR signal pathways and protein translation in the rat frontal cortex

• Published in: Progress in neuro-psychopharmacology & biological psychiatry Vol. 45; pp. 73 - 82
• Main Authors: Kim, Se Hyun, Yu, Hyun-Sook, Park, Hong Geun, Ha, Kyooseob, Kim, Yong Sik, Shin, Soon Young, Ahn, Yong Min
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.08.2013; Elsevier
• Subjects: Adult and adolescent clinical studies; AKT protein; Animals; Biological and medical sciences; Bipolar disorder; Bipolar disorders; Carrier Proteins - metabolism; Enzyme Inhibitors - administration & dosage; Enzyme Inhibitors - pharmacology; Eukaryotic Initiation Factors - metabolism; Frontal Lobe - drug effects; Frontal Lobe - metabolism; Injections, Intraventricular; Male; Medical sciences; Mood disorders; Motor Activity - drug effects; Na-pump; Ouabain - administration & dosage; Ouabain - pharmacology; p70S6K; Phosphoproteins - metabolism; Phosphorylation - drug effects; Protein Biosynthesis - drug effects; Protein synthesis; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Rats; Ribosomal Protein S6 Kinases, 70-kDa - metabolism; Ribosome Subunits, Small - metabolism; Signal Transduction - drug effects; Sodium-Potassium-Exchanging ATPase - antagonists & inhibitors; TOR Serine-Threonine Kinases - metabolism; eIF4B; p70S6K; S6; BDNF; PLC; Na/K-ATPase; DAPI; PKC; Bipolar disorder; MAPK; EGFR; ANOVA; OD; Protein synthesis; 4E-BP; PMS; aCSF; mTOR; NMDA; Na-pump; ICV; ERK; Animal model; Cardiotonic agent; Rat; Central nervous system; Ouabain; Frontal cortex; K; Encephalon; Na; mTOR inhibitor; Glycoside; Mood disorder; Enzyme; Rodentia; Enzyme inhibitor; Cerebral ventricle; Genetic translation; Protein; Vertebrata; Mammalia; Animal; Intracerebral administration; Mania; Hydrolases; exchanging ATPase; sodium and potassium-activated adenosine triphosphatase; eukaryotic translation initiation factor 4E binding protein; eukaryotic translation initiation factor 4B; mitogen-activated protein kinase; small ribosomal protein 6; analysis of variance; intracerebroventricular; mammalian target rapamycin; brain-derived neurotrophic factor; protein kinase C; extracellular signal regulated kinase; phospholipase C; postmitochondrial supernatant; epidermal growth factor receptor; 4′,6′-diamidino-2-phenylindole; artificial cerebrospinal fluid; n-methyl-d-aspartate; p70 ribosomal S6 kinase; optical density
• ISSN: 0278-5846; 1878-4216
• DOI: 10.1016/j.pnpbp.2013.04.018

Intracerebroventricular (ICV) injection of ouabain, a specific Na/K-ATPase inhibitor, induces behavioral changes in rats in a putative animal model of mania. The binding of ouabain to Na/K-ATPase affects signaling molecules in vitro, including ERK1/2 and Akt, which promote protein translation. We have also reported that ERK1/2 and Akt in the brain are involved in the ouabain-induced hyperactivity of rats. In this study, rats were given an ICV injection of ouabain, and then their frontal cortices were examined to determine the effects of ouabain on the mTOR/p70S6K/S6 signaling pathway and protein translation, which are important in modifications of neural circuits and behavior. Rats showed ouabain-induced hyperactivity up to 8h following injection, and increased phosphorylation levels of mTOR, p70S6K, S6, eIF4B, and 4E-BP at 1, 2, 4, and 8h following ouabain injection. Immunohistochemical analyses revealed that increased p-S6 immunoreactivity in the cytoplasm of neurons by ouabain was evident in the prefrontal, cingulate, and orbital cortex. These findings suggested increased translation initiation in response to ouabain. The rate of protein synthesis was measured as the amount of [3H]-leucine incorporation in the cell-free extracts of frontal cortical tissues, and showed a significant increase at 8h after ouabain injection. These results suggest that ICV injection of ouabain induced activation of the protein translation initiation pathway regulated by ERK1/2 and Akt, and prolonged hyperactivity in rats. In conclusion, protein translation pathway could play an important role in ouabain-induced hyperactivity in a rodent model of mania. •Intrabrain injection of ouabain induces hyperactivity of rats.•Ouabain increases mTOR/p70S6K/S6 phosphorylation in rat frontal cortex.•Activation of S6 is evident in cytoplasm of neurons in frontal cortex.•Ouabain up-regulates protein synthesis rate in frontal cortical tissue.