Contents lists available at ScienceDirect Journal of Chemical Neuroanatomy journal homepage: www.elsevier.com/locate/jchemneu Changes in the element concentration of the dorsal hippocampus CA1 region during memory consolidation and reconsolidation Paulo Fernandes Costa Jobim a, ⁎ , Carla Eliete Iochims dos Santos b , Luka Jeromel c , Primoz Pellicon c , Livio Amaral d , Johnny Ferraz Dias d a Physiology Department, Federal University of Health Sciences of Porto Alegre, Rua Sarmento Leite 245, CEP 90050-170, Porto Alegre, RS, Brazil b Institute of Physics, Statistics and Mathematics, Federal University of Rio Grande, CEP 95500-000, Santo Antônio da Patrulha, RS, Brazil c Department for Low and Medium Energy Physics, Jožef Stefan Institute, SI-1000, Ljubljana, Slovenia d Ion Implantation Laboratory, Institute of Physics, Federal University of Rio Grande do Sul, Av. Bento Gonçalves 9500, CP 15051, CEP 91501-970, Porto Alegre, RS, Brazil ARTICLE INFO Keywords: PIXE Ion beam techniques Aversive memory Brain element composition ABSTRACT The concentration and distribution of Mg, P, Cl, K, Cu and Zn in the dorsal hippocampus CA1 region of rat brains were studied during memory consolidation and reconsolidation processes stimulated with inhibitory avoidance (IA) tests. Experimental rats were divided into four groups: i) group not submitted to inhibitory avoidance task (IA-N); ii) group submitted to inhibitory avoidance training session (IA-Y); iii) group submitted to inhibitory avoidance reactivation session but did not step down from the platform (IAR-N); and iv) group submitted to avoidance reactivation session and stepped down from the platform (IAR-Y). Elemental concentration and dis- tribution in the CA1 hippocampus region were obtained through the Particle-Induced X-ray Emission (PIXE) technique. The results indicate that the concentration of Mg, P, Cl, K and Cu increased during memory con- solidation. During the memory reconsolidation process, the concentrations of Mg, P, Cl and K increased, while Cu and Zn had no significant changes with respect to their basal condition. These results show that the major part of these elements may be engaged in memory consolidation could be also participating in memory re- consolidation. For all elements, the general trend related to their concentration did not change during re- consolidation regardless the presence of a novelty event, i.e. stepping down from the platform. 1. Introduction Memory can be defined as the ability to acquire, store and recall information. The acquisition phase represents the time when new in- formation is acquired. It involves the transport of elements through neuron’s membrane and requires the participation of several signaling pathways in order to store the memory permanently (Lamprecht and Ledoux, 2004). The molecular activity related with early stages of memory takes place into the hippocampus and it is known as con- solidation (Dudai, 2004). Memory consolidation is a complex process regulated by a series of biochemical reactions leading to progressive post-acquisition memory stabilization (Jobim, 2011). Consolidated memories become again labile and susceptible to intervention when reactivated. To keep the memory activated, it is necessary to go through a new process of stabilization called reconsolidation (Lee, 2008). The reconsolidation provides a window of opportunities for the main- tenance and strengthening of the evoked mnemonic trace. Many treatments used to block consolidation can impair reconsolidation, which leads to the hypothesis that the reconsolidation leads mostly to the same molecular event that took place during consolidation. But even with some similarities, consolidation and reconsolidation pro- cesses are not identical (Alberini, 2005). As a matter of fact, some studies pointed out that some proteins are synthesized specifically during consolidation while some others are synthesized specifically during reconsolidation, thus revealing their different molecular profiles (Tronel et al., 2005). In addition, the timing and purpose of these two processes are also different since consolidation gives rise to new memories after acquisition while reconsolidation works as a memory update in a post-reactivation stage (Lee, 2010). There are also limiting factors for reconsolidation which may prevent it from happening (Lee, 2009). Recent studies have shown the importance of chemical elements to the synapse plasticity and particularly to the memory consolidation. For instance, the influx of Ca into post-synaptic neurons through N-methyl- https://doi.org/10.1016/j.jchemneu.2017.12.003 Received 19 September 2017; Received in revised form 12 December 2017; Accepted 13 December 2017 ⁎ Corresponding author. E-mail addresses: paulojobim@live.com (P.F.C. Jobim), carlaiochims@furg.br (C.E.I. dos Santos), luka.geromel@ijs.si (L. Jeromel), primoz.pelicon@ijs.si (P. Pellicon), amaral@if.ufrgs.br (L. Amaral), jfdias@if.ufrgs.br (J.F. Dias). Journal of Chemical Neuroanatomy 90 (2018) 49–56 Available online 14 December 2017 0891-0618/ © 2017 Elsevier B.V. All rights reserved. T