Neuropharmacology and Analgesia Changes in the level of calcyon mRNA in the brain of rats exposed to cocaine, self-administered or received passively Agata Faron-Górecka, Magdalena Gąska, Maciej Kuśmider, Małgorzata Frankowska, Przemysław Adamczyk, Małgorzata Filip, Marta Dziedzicka-Wasylewska ⁎ Institute of Pharmacology, Polish Academy of Sciences, 12 Smętna Street, Kraków, Poland abstract article info Article history: Received 16 November 2009 Received in revised form 13 January 2010 Accepted 3 February 2010 Available online 17 February 2010 Keywords: Calcyon Cocaine self-administration In situ hybridization (Rat) The level of mRNA encoding calcyon (measured by in situ hybridization), one of the dopamine receptor interacting proteins, has been examined in the rat brain in the established animal model used to study the mechanisms of cocaine addiction (cocaine self-administration involving a yoked procedure). Two weeks of cocaine self-administration (maintenance) did not affect the level of calcyon mRNA, regardless of the way cocaine was delivered, except for tuberculum olfactorium, where calcyon mRNA was increased after cocaine treatment. In the reinstatement phase of the experiment cocaine alone induced an increase in the calcyon mRNA expression in most of the brain region studied (caudate putamen; tuberculum olfactorium; paraven- tricular thalamic nucleus; ventromedial hypothalamic nucleus and paraventricular hypothalamic nucleus) but only in the yoked saline control group. In other words, these results show that the single dose of cocaine (10 mg/kg) was able to induce an alteration in the level of calcyon mRNA in these rats which never before experienced any cocaine administration. The most significant effects were observed in the ventromedial hypothalamic nucleus and paraventricular hypothalamic nucleus. Interestingly, a similar effect was observed when the reinstatement of cocaine-seeking behaviour was evoked by cue (conditioned stimuli) that indicates that no cocaine was necessary to induce the changes in the level of calcyon mRNA expression. This effect was significant in tuberculum olfactorium, ventromedial hypothalamic nucleus and paraventricular hypothalamic nucleus. Such a result together with the brain areas involved in these effects might suggest the role of calcyon similar to the CART peptides and special vulnerability of calcyon expression rather to acute than chronic stimuli. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Calcyon is a transmembrane protein with a predicted single transmembrane segment, mainly localized to intracellular vesicles of dendritic spines (Lezcano et al., 2000). Recently Zelenin et al. (2002) have shown that rat calcyon mRNA is expressed only in the brain and not in other tissues studied (as for example kidney cortex and medulla, lung, heart, liver). Brain-specific expression of calcyon is strong and distinct in various areas, especially in the hippocampus and hypothal- amus (Oakman and Meador-Woodruff, 2004). It has been shown that calcyon modulates the binding properties of the dopamine D 1 receptor and may play a role in intracellular calcium signalling mediated by that receptor (Lezcano et al., 2000). Calcyon protein has been also indicated as a modulator of dopamine D 1 receptor sensitivity for ligands (Lidow et al., 2001). Among the various brain functions in which the dopamine D 1 receptor has been involved, its role in cocaine addiction has been also strongly indicated (Xu et al., 1994; Hummel and Unterwald, 2002; Anderson and Pierce, 2005). It has been shown that the D 1 receptor mediates cocaine-induced reinforcement and reward (Weed and Woolverton, 1995), behavioural sensitization and also changes in gene expression (Zhang et al., 2002). Calcyon has been shown to be co-expressed with the dopamine D 1 receptor in various brain regions (Zelenin et al., 2002), which enables the interaction between these two proteins. It suggests, in turn, the potential role of calcyon in various D 1 -mediated processes, including – among others – reinforcement and reward, behavioural sensitization and locomotor activity. Therefore we decided to study the changes in the level of mRNA encoding calcyon in three phases of cocaine self- administration in the well established model involving a “yoked” procedure (Frankowska et al., 2008a, b) in which each experimental animal (working actively to get cocaine) was paired with 2 rats serving as a “yoked” control — one receiving cocaine passively and the other one receiving saline. European Journal of Pharmacology 634 (2010) 33–39 ⁎ Corresponding author. Department of Pharmacology, Polish Academy of Sciences, 12 Smętna Street, PL-31-343 Kraków, Poland. Tel.: + 48 12 662 33 72; fax: + 48 12 637 45 00. E-mail address: wasyl@if-pan.krakow.pl (M. Dziedzicka-Wasylewska). 0014-2999/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.ejphar.2010.02.010 Contents lists available at ScienceDirect European Journal of Pharmacology journal homepage: www.elsevier.com/locate/ejphar