Zinc deficiency in rats is associated with up-regulation of hippocampal NMDA receptor Urszula Doboszewska a , Magdalena Sowa-Kućma a , Katarzyna Młyniec b , Bartłomiej Pochwat a , Malgorzata Hołuj c , Beata Ostachowicz d , Andrzej Pilc a,e , Gabriel Nowak a,b , Bernadeta Szewczyk a, ⁎ a Department of Neurobiology, Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, PL 31-343 Kraków, Poland b Faculty of Pharmacy, Jagiellonian University Medical College, Medyczna 9, PL 30-688 Kraków, Poland c Department of Behavioral Neuroscience & Drug Development, Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, PL 31-343 Kraków, Poland d Faculty of Physics and Applied Computer Sciences, AGH University of Science and Technology, Mickiewicza 30, PL 30-059 Kraków, Poland e Faculty of Health Sciences, Jagiellonian University Medical College, Michałowskiego 20, PL 31-126 Kraków, Poland abstract article info Article history: Received 1 July 2014 Received in revised form 31 August 2014 Accepted 19 September 2014 Available online 5 October 2014 Keywords: Forced swim test NMDA receptor Social interaction test Sucrose intake test Zinc deficiency Rationale: Data indicated that zinc deficiency may contribute to the development of depression; however changes induced by zinc deficiency are not fully described. Objectives: In the present paper we tested whether the dietary zinc restriction in rats causes alterations in N-methyl-D-aspartate receptor (NMDAR) subunits in brain regions that are relevant to depression. Methods: Male Sprague Dawley rats were fed a zinc adequate diet (ZnA, 50 mg Zn/kg) or a zinc deficient diet (ZnD, 3 mg Zn/kg) for 4 or 6 weeks. Then, the behavior of the rats was examined in the forced swim test, sucrose intake test and social interaction test. Western blot assays were used to study the alterations in NMDAR subunits GluN2A and GluN2B and proteins associated with NMDAR signaling in the hippocampus (Hp) and prefrontal cortex (PFC). Results: Following 4 or 6 weeks of zinc restriction, behavioral despair, anhedonia and a reduction of social behav- ior occurred in rats with concomitant increased expression of GluN2A and GluN2B and decreased expression of the PSD-95, p-CREB and BDNF protein levels in the Hp. The up-regulation of GluN2A protein was also found in the PFC, but only after prolonged (6 weeks) zinc deprivation. Conclusions: The procedure of zinc restriction in rats causes behavioral changes that share some similarities to the pathophysiology of depression. Obtained data indicated that depressive-like behavior induced by zinc deficiency is associated with the changes in NMDAR signaling pathway. © 2014 Elsevier Inc. All rights reserved. 1. Introduction Depression is a chronic debilitating disorder with an increasing prevalence (WHO, 2008). It has a neurobiological basis and is associated with functional and structural brain abnormalities, e.g., neuroimaging studies have established the relevance of the prefrontal cortex (PFC) and the hippocampus (Hp) to major depression (Kupfer et al., 2012; Palazidou, 2012). The first line-medications for major depressive disor- der (MDD) are based on the monoamine hypothesis of depression and antidepressant action (Coppen, 1967; Schildkraut, 1965), have a delayed onset of action, and fail to produce a response in a large percent of patients (Trivedi et al., 2006). In contrast, the infusion of subanaesthetic doses of the N-methyl-D-aspartate receptor (NMDAR) antagonist ketamine exerts rapid antidepressant effects in patients with treatment resistant MDD (Aan Het Rot et al., 2012; Berman et al., 2000; Zarate et al., 2006). These observations suggest that strategies be- yond the monoaminergic system might be beneficial for improving the treatment outcome in depressed patients. Exploring glutamatergic tar- gets, including NMDAR, may be a promising approach to the discovery of novel antidepressants (Pilc et al., 2013). Furthermore, magnetic reso- nance spectroscopy studies have shown altered levels of glutamate in the central nervous system of depressed patients (Grimm et al., 2012). These data strongly support the hypothesis that the glutamatergic sys- tem and NMDAR play an important role in the pathophysiology and treatment of depression (Skolnick et al., 2009). The NMDAR functions as a heteromeric complex composed of four subunits surrounding a central cation-selective pore. Three major sub- types of NMDAR subunits have been described: GluN1, GluN2A–D and GluN3A–B(Cull-Candy et al., 2001). The most widely expressed Progress in Neuro-Psychopharmacology & Biological Psychiatry 56 (2015) 254–263 Abbreviations: CaMK, Ca 2+ calmodulin-dependent protein kinase; CMS, chronic mild stress; CREB, cyclic AMP response element binding protein; CUS, chronic unpredictable stress; BDNF, brain-derived neurotrophic factor; FST, forced swim stress; Hp, hippocampus; MDD, major depressive disorder; p-CREB, phosphorylated CREB; NMDAR, N-methyl-D-as- partate receptor; PFC, prefrontal cortex; p-TrkB, phosphorylated TrkB; PSD, postsynaptic density; PSD-95, postsynaptic density protein 95; TrkB, tropomyosine-related kinase B re- ceptor; TXRF, Total Reflection X-Ray Fluorescence; ZnA, zinc adequate; ZnD, zinc deficient. ⁎ Corresponding author. Tel.: +48 126623362; fax: +48 126374500. E-mail address: szewczyk@if-pan.krakow.pl (B. Szewczyk). http://dx.doi.org/10.1016/j.pnpbp.2014.09.013 0278-5846/© 2014 Elsevier Inc. All rights reserved. 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