Behavioural Pharmacology Protective effects of saffron extract and its active constituent crocin against oxidative stress and spatial learning and memory deficits induced by chronic stress in rats Behshid Ghadrdoost a , Abbas Ali Vafaei a, 1 , Ali Rashidy-Pour a, ⁎, Razieh Hajisoltani a , Ahmad Reza Bandegi b, 1 , Fareshteh Motamedi c , Saeed Haghighi d , Hamid Reza Sameni d , Sharzad Pahlvan d a Laboratory of Learning and Memory, Research Center and Department of Physiology, School of Medicine, Semnan University of Medical Sciences, Semnan, Iran b Laboratory of Endocrine Research, Department of Biochemistry, School of Medicine, Semnan University of Medical Sciences, Semnan, Iran c Neuroscience Research Center, Shaheed Beheshti University of Medical Sciences, Tehran, Iran d Department of Histology, School of Medicine, Semnan University of Medical Sciences, Semnan, Iran abstract article info Article history: Received 11 December 2010 Received in revised form 21 April 2011 Accepted 3 May 2011 Available online 18 May 2011 Keywords: Chronic stress Spatial learning Spatial memory Saffron Crocin Oxidative stress Although it is well established that chronic stress impairs spatial learning and memory, few studies have investigated possible ways to prevent its deleterious effects. Here, we investigated the effects of Crocus sativus L., commonly known as saffron, and its active constituent crocin on learning and memory loss and the induction of oxidative stress in the hippocampus by chronic stress. Rats were injected with saffron extract, crocin or vehicle over a period of 21 days while being exposed to chronic restraint stress (6 h/day). After this, they were trained and tested on a water-maze spatial memory task. They performed four trials per day for 5 consecutive days, and this was followed by a probe trial two days later. At the end of the behavioral testing, several parameters of oxidative stress in the hippocampus were measured. Treatment with saffron extract or crocin blocked the ability of chronic stress to impair spatial learning and memory retention. Relative to controls that received vehicle, stressed animals that received saffron extract or crocin had significantly higher levels of lipid peroxidation products, significantly higher activities of antioxidant enzymes including glutathione peroxidase, glutathione reductase and superoxide dismutase and significantly lower total antioxidant reactivity capacity. Finally, crocin significantly decreased plasma levels of corticosterone, as measured after the end of stress. These observations indicate that saffron and its active constituent crocin can prevent the impairment of learning and memory as well as the oxidative stress damage to the hippocampus induced by chronic stress. Thus, using these substances may be useful in pharmacological alleviation of cognitive deficits. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Chronic stress has been reported to impair spatial learning and memory in a variety of spatial tasks. This effect is mediated mainly via the elevation of glucocorticoid levels (Conrad, 2010). It is well known that stress triggers the activation of the hypothalamus–pituitary– adrenal (HPA) axis, culminating in the production of glucocorticoids by the adrenals glands. Receptors for these steroids are expressed throughout the brain, and expression is particularly strong in brain structures involved in cognition and mental health, including the hippocampus (De Kloet et al., 1987; Reul and De Kloet, 1985). Glucocorticoids can have short and long-lasting effects on behavior and cognitive functions via genomic and non-genomic mechanisms (Haller et al., 2008; Lupien et al., 2009). In fact, chronic stress induces a series of morphological changes in the hippocampi of rats and primates. These alterations include retraction of the apical dendrites in the CA3 region of the hippocampus, modification of hippocampal dendritic spine number and shape, and cell death (Conrad et al., 2007; Kleen et al., 2006). These structural and functional changes of the hippocampus following chronic stress may contribute to the impair- ment of cognitive functions (McLaughlin et al., 2007). While stress- induced memory impairments have been extensively studied (Conrad, 2010), very few studies have examined possible ways of preventing the deleterious effects of stress. Oxidative stress is caused by an imbalance between the production of reactive oxygen species and a biological system's ability to detoxify the reactive intermediates or easily repair the resulting damage (Sies, 1997; Storz and Imlay, 1999). Oxidative stress is an important mechanism that may contribute to the cytotoxicity and impairment of learning and memory induced by chronic stress (Muriach et al., 2010; Palumbo et al., 2007; Sharma et al., 2009). Oxidative stress has been implicated in the pathophysiology of several neurodegenerative European Journal of Pharmacology 667 (2011) 222–229 ⁎ Corresponding author at: Laboratory of Learning and Memory, Research Center and Department of Physiology, Semnan University of Medical Sciences P. O. Box: 35145-331, Semnan, Iran. Tel./fax: +98 231 3354186. E-mail address: Rashidy-pour@sem-ums.ac.ir (A. Rashidy-Pour). 1 Equal contribution to the work with the first author. 0014-2999/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ejphar.2011.05.012 Contents lists available at ScienceDirect European Journal of Pharmacology journal homepage: www.elsevier.com/locate/ejphar