Behavioural Processes 99 (2013) 130–137 Contents lists available at ScienceDirect Behavioural Processes journal homepage: www.elsevier.com/locate/behavproc The role of pregnenolone sulphate in spatial orientation-acquisition and retention: An interplay between cognitive potentiation and mood regulation ∗ Fulvio Plescia, Rosa A.M. Marino, Emanuele Cannizzaro, Anna Brancato, Carla Cannizzaro Department of Sciences for Health Promotion and Mother and Child Care “Giuseppe D’Alessandro”, University of Palermo, V. Vespro 129, 90127 Palermo, Italy a r t i c l e i n f o a b s t r a c t Article history: Neurosteroids can alter neuronal excitability interacting with specific neurotransmitter receptors, thus Received 23 May 2013 affecting several functions such as cognition and emotionality. In this study, we investigated, in adult Received in revised form 4 July 2013 male rats, the effects of the acute administration of pregnenolone-sulfate (PREGS) (10 mg/Kg, s. c.) on Accepted 5 July 2013 cognitive processes using the Can test, a non aversive spatial/visual task which allows the assessment of spatial information-acquisition during the baseline training, and of memory retention in the longitudi- Keywords: nal study. Furthermore, on the basis of PREGS pharmacological profile, the modulation of depressive-like Pregnenolone-sulphate behaviour was also evaluated in the forced swim test (FST). Our results indicate that acute PREGS induces: Spatial orientation-acquisition an improvement in spatial orientation-acquisition and in reference memory, during the baseline training; Spatial orientation-retention a strengthening effect on reference and working memory during the longitudinal study. A decrease in Cognitive map Depressive-like behaviour immobility time in the FST has also been recorded. In conclusion, PREGS exerts enhancing properties on acquisition, consolidation and retrieval of spatial information, probably due of improved hippocampal- dependent memory processes. The additional antidepressant effect observed in the FST can provide further evidence in support of the potential of PREGS as a therapeutic tool for the treatment of cognitive deficits associated with mood disorders. This article is part of a Special Issue entitled: insert SI title. © 2013 Elsevier B.V. All rights reserved. 1. Introduction main inhibitory neurotransmitter receptor in the nervous system, ␥ the -amimobutyric acid receptor (GABAA), and because it posi- A variety of neuroactive steroids may be synthesized in the tively regulates the ionotropic glutamate receptor family of ligand brain itself, from cholesterol, without the aid of peripheral sources: gated ion channels such as N-methyl-d-aspartate receptor (NMDA) they have been named “neurosteroids”, a variety of pleiotropic and amino-3-hydroxy-5methyl-4-isoxazole propionic acid (AMPA) molecules that act through both genomic and non genomic mech- receptors (Akk et al., 2001; Gibbs and Farb, 2004; Gibbs et al., anisms, broadly affecting several behavioural functions (Baulieu, 2006; Wang et al., 2007); it also enhances glutamatergic trans- 1998; Vallée et al., 2001a,b). Among them, pregnenolone and mission by acting on presynaptic sigma-1-like receptors (Meyer its sulfated ester pregnenolone sulfate (PREGS) have been mea- et al., 2002; Schiess and Partridge, 2005). PREGS plays a critical sured in human plasma and brain tissue (Schumacher et al., 2008) role in several physiological and paraphysiological processes such and, despite lacking hormonal action, they still affect neuronal as sleep modulation (Darnaudéry et al., 2000; Darbra et al., 2004), excitability through the modulation of ionotropic receptors. From emotionality, memory performance, and in age-related neuropsy- a pharmacological point of view, PREGS qualified as an “excit- chiatric disorders (Reddy and Kulkarni, 1997, 1998; Reddy et al., atory neuroactive steroid”, because it negatively modulates the 1998; Urani et al., 2001; Phan et al., 2002; Longone et al., 2008). Indeed, decreased concentrations of this neurosteroid have been detected in patients suffering from Alzheimer’s disease and multi- infarct dementia, as well as in depression (Näsman et al., 1991; ∗ Corresponding author at: University of Palermo, Department of Sciences for Hillen et al., 2000; Van Broekhoven and Verkes, 2003). These data Health Promotion and Mother and Child Care “G. D’Alessandro”, Laboratory of Neu- support the hypothesis that the most prominent, as well as the most ropsychopharmacology, Via del Vespro 129, 90127 Palermo, Italy. proficuous, functions of PREGS deal with the positive modulation of E-mail addresses: [email protected], mood and cognition in humans and in animals (Flood et al., 1988, [email protected] (C. Cannizzaro). 0376-6357/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.beproc.2013.07.001 F. Plescia et al. / Behavioural Processes 99 (2013) 130–137 131 1992, 1995; Vallée et al., 1997, 2001b; Mayo et al., 1993; Reddy, the Council Directives on the matter (No. 2010/63/EU). All possible 2011). We usually identify animal cognitive functions as learn- efforts were made to minimize animal pain and discomfort and to ing and memory: a complex set of neural dynamic processes that reduce the number of experimental subjects. mainly consist on acquisition, storage and retrieval of information (Thorpe, 1956; Dudai, 1989). These two differential and comple- 2.3. Pharmacological treatment mentary functions can be studied in the animal model in order to get information on the neuronal circuitries involved, as well as on Rats were injected with PREGS (Sigma-Aldrich SRL, Milan, Italy) the effects of drugs acting in the central nervous system. The forma- (10 mg/kg; n = 16) or vehicle (0.1% Tween 80; n = 16) on the day of tion and storage of long-term declarative memory broadly depend behavioural testing. PREGS was dissolved in 0.1% Tween 80, and on the interaction between the hippocampus, a region anatomi- injected (1 ml/kg subcutaneously) two hours before each exper- cally related to the medial temporal lobe, and the neocortex (Squire imental session, in order to observe a minor inter-individual and Zola-Morgan, 1991; Eichenbaum, 1991). While in humans the variability of the effects. Control rats received the same volume form of memory that strictly depends on the hippocampus is the (1 ml/kg) of the vehicle at the same time. In this study, we used a episodic memory (Amaral et al., 1987), in animals the hippocampus single dose of PREGS known to induce the most prominent effects undoubtedly plays a very important role in orientation, in space and on different behavioural patterns (Yang et al., 2012; Reddy and in the construction of cognitive maps (Morris et al., 1982; Cain and Kulkarni, 1998). Saucier, 1996; O’Keefe and Dostrovsky, 1971; O’Keefe and Nadel, 1978), engaging the basal forebrain cholinergic system and its tar- 2.4. Neurocognitive testing get structures (Deiana et al., 2011). Spatial learning and memory can be dissected through application of several maze tasks, includ- 2.4.1. Experimental design ing radial arm maze, Y-maze and the water maze, and recently by Learning and memory functions were assessed by training the the Can test. This is a validated, non aversive reward-facilitated animals in the Can test, a novel motivated, non-aversive spatial- task which enables the study of the spatial and visual abilities of object discrimination task, developed by Popovic¸ et al. (2001) the animals, assessing in the same task both working memory, and Popovic¸ et al. (2006) and further employed in our previ- – the temporary storage and manipulation of information – and ous studies (Cannizzaro et al., 2005; Cannizzaro et al., 2006, reference-memory, as a measure of a long-term stable memory 2007). The behavioural protocol consisted of three separate parts: traces (Baddeley and Hitch, 1974; Goldman-Rakic, 1996; Fuster, shaping period; spatial orientation-acquisition; spatial orientation- 2001; Dudchenko, 2004; Popovic¸ et al., 2006). Thus, given these retention. The experiments were performed under 100lux light premises, the aim of this research is to analyze the potential effect of intensity. PREGS as cognitive enhancer, evaluating its activity during the dif- ferent phases of learning and memory: acquisition, consolidation 2.4.2. The Can test and retrieval of spatial information in the Can test. Moreover, on The tops of seven soft-drink cans were removed. Cans were the basis of the pharmacological profile of PREGS, and since several painted in white or left in their imprinted colours according to the reports show that neurocognitive deficits are comorbid with affec- task administered. The cans were put upside down in a square plex- tive disorders in humans (McIntyre et al., 2013; Godard et al., 2012; iglas compartment (100 cm × 100 cm × 43 cm). This allowed their Sanchez-Moreno et al., 2009), the modulation of depressive-like indented bottoms to hold water. The cans were placed on a solid behaviour was also evaluated in the forced swim test. pedestal, which elevated the upper edge of the can to a height of 14 cm. The cans were arranged in a fan shaped pattern, in which the distance from each can to a start point was 70 cm and the distance 2. Methods between the cans was 7 cm. In the task, rats were trained to iden- tify a single rewarded can among a set of seven cans. The reward 2.1. Animals consisted of 0.3 ml of tap water, using 23 h water deprivation sched- ule for motivation. When the rat stood on its hind paws and brought Experiments were carried out on adult male Wistar rats (initial its nose up to the level of the top edge of the can, this was considered weight 200–250, Harlan, Udine, Italy). The animals were housed in ◦ a “visit”. The parameters measured were: (1) “activity”, the num- a standard plastic cages, two per cage, in a temperature (22 ± 2 C) ber of trials on which rats visited at least one can (up to 10 during – and humidity (55 ± 10%) – controlled room.