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Advances in Pharmacological Sciences
Volume 2012 (2012), Article ID 494367, 7 pages
http://dx.doi.org/10.1155/2012/494367
Research Article

Effect of Aqueous Extract of Crocus sativus L. on Morphine-Induced Memory Impairment

1Neuroscience Research Center and Department of Physiology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
2Pharmacological Research Center of Medicinal Plants and Department of Pharmacology, School of Medicine, Mashhad University of Medical Sciences, Mashhad 9177948564, Iran

Received 9 July 2012; Revised 11 September 2012; Accepted 11 September 2012

Academic Editor: Karim A. Alkadhi

Copyright © 2012 Sayede Maryam Naghibi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

In the present study, the effect of aqueous extracts of saffron on morphine-induced memory impairment was investigated. On the training trial, the mice received an electric shock when the animals were entered into the dark compartment. Twenty-four and forty-eight hours later, the time latency for entering the dark compartment was recorded and defined as the retention trial. The mice were divided into (1) control, (2) morphine which received morphine before the training in the passive avoidance test, (3–5) three groups treated by 50, 150 and 450 mg/kg of saffron extract before the training trial, and (6 and 7) the two other groups received 150 and 450 mg/kg of saffron extract before the retention trial. The time latency in morphine-treated group was lower than control (P < 0.01). Treatment of the animals by 150 and 450 mg/kg of saffron extract before the training trial increased the time latency at 24 and 48 hours after the training trial (P < 0.05 and P < 0.01). Administration of both 150 and 450 mg/kg doses of the extract before retention trials also increased the time latency (P < 0.01). The results revealed that the saffron extract attenuated morphine-induced memory impairment.

1. Introduction

Crocus sativus L. is a plant with green and hairy leaves and funnel-shaped reddish-purple flowers, which is cultivated in some countries including China, Spain, Italy, Greece, and especially Iran. It is commonly known as saffron or “Zaaferan” in Iran and is added to food for its color and taste [1, 2]. The part used for medication is the central part of the flower or the female sexual organ which is also called stigma or style. The main active constituents of this plant are picrocrocin and its derivatives include safranal, flavonoid derivatives, and crocin [3]. Safranal is the main aromatic component of saffron which comprises about 60% of the volatile ingredients in saffron [4]. Crocus sativus is used in folk medicine as an antispasmodic, eupeptic, anticatarrhal, carminative, diaphoretic, expectorant, stimulant, stomachic, aphrodisiac, emmenagogue gingival, and sedative [3].

It has been reported that extracts of Crocus sativus prevent from scopolamine and ethanol-induced memory impairment in Morris water maze and passive avoidance tests. It also protects against ethanol-induced inhibition of hippocampal long-term potentiation (LTP) [5, 6]. In addition, it has been reported that crocin counteracts the ethanol inhibition of NMDA receptor-mediated responses in rat hippocampal neurons [7]. It has been also shown that saffron attenuates cerebral ischemia [8] and reduces the extracellular hippocampal levels of glutamate and aspartate [9]. Saffron extracts or its active constituents have other activities on the central nervous system including antidepressant [10, 11], anticonvulsant [12, 13], and anxiolytic and hypnotic [14]. Some actions of saffron on central nervous system have been attributed to its effects on opioid system [12]. It has been also demonstrated that aqueous and ethanolic extracts of Crocus sativus stigma and its constituent crocin can suppress morphine withdrawal syndrome [1].

Learning and memory in laboratory animals are known to be affected by opioids and their antagonists [15]. For example, pretraining administration of morphine impairs memory retrieval in passive avoidance tests which will be restored by pretest administration of the same dose of morphine [16]. Hippocampus is one of the areas involved in learning and memory in which both opioid peptides and opioid receptors are expressed [17]. Endogenous opioid peptides consider important neuromodulators in the brain, which are rich in the hippocampus and cerebral cortex [18]. Using different animal models, it was shown that repeated administering morphine can impair memory and learning processes [17, 19, 20].

With regard to the effects of saffron on learning and memory and its interactions with opioid system, the aim of the present study was to evaluate the effect of aqueous extract of Crocus sativus L. on morphine-induced memory impairment in mice using the passive avoidance test.

2. Materials and Methods

2.1. Preparing the Plant Extract

In this study, saffron was kindly provided by Novin Zaafran Company, Mashhad, Iran. The powder (100 g) of saffron was extracted with distilled water in a Soxhlet apparatus for 72 h. The resulting extract was concentrated under reduced pressure and kept at −20°C until being used (yielded 33.2%). The extract was dissolved in saline and was then applied [2123].

2.2. Animals and the Experimental Protocol

Seventy-two male mice (30 ± 5 g, 10 weeks old) were kept at 22 ± 2°C and 12 h light/dark cycle (light on at 7:00 AM). All behavioral experiments were carried out between 10 AM and 2 PM The experiments were conducted in accordance with the Guide for the Care and Use of Laboratory Animals and the study was approved by Mashhad University of Medical Sciences. In the present study, the effects of the extract were examined in 2 experiments. In Experiment 1, the extract was injected before training phase (pretraining effect), while in Experiment 2 the extract was administered 24 and 48 hours after training phase (before the test phase, pretest effect).

Experiment 1
In this experiment the pretraining effect of the extract was examined. The animal groups were as follows. (1) Control group ( ): the animals in this group received saline instead of both the saffron extract and morphine. (2) Morphine group ( ): the animals were treated by saline instead of saffron extract, but morphine was injected to them (5 mg/kg, s.c.) 30 min before the training phase. (3–5) Pretraining treated groups ( in each group) (pretrain 50, pretrain 150, and pretrain 450): the animals in these groups were daily treated by 50, 150, and 450 mg/kg of saffron extract (i.p.), respectively, for 3 days before the training phase.

Experiment 2
In this experiment the pretest effect of the extract was examined. The animal groups were as follows. (1) Control group ( ): the animals in this group received saline instead of both saffron extract and morphine. (2) Morphine group ( ): the animals were treated by saline instead of saffron extract before the retention phase, but morphine was injected to them (5 mg/kg, s.c.) 30 min before the training phase. (3–4) Pretest groups ( in each group) (pretest 150 and pretest 450): the animals in these groups received 150 and 450 mg/kg of saffron extract (i.p.), respectively, before the test phase (24 and 48 hours after training phase).

2.3. Behavioral Procedures

The animals were handled for 1week before starting the experiments. A passive avoidance learning test based on negative reinforcement was used to examine the memory. The apparatus consisted of a light and a dark compartment with a grid floor adjoining each other through a small gate. The animals were accustomed to the behavioral apparatus during two consecutivedays (5 min in each day) before the training session. On the third day, the animals were placed in the light compartment, and the time latency for entering the dark compartment was recorded. In the training phase, the mice were placed in the light compartment facing away from the dark compartment. When the animals were entered completely into the dark compartment, they received an electric shock (1 MA, 2 s duration). The mice were then returned to their home cage. Twenty-four and forty-eight hours later (the retention phase or test phase), the animals were placed in the light compartment, and the time latency for entering the dark compartment as well as the time spent by the animals in the dark and light compartments was recorded and defined as the retention trial [24, 25].

2.4. Statistical Analysis

The data were expressed as mean ± SEM. The statistical analysis was done by one-way ANOVA followed by a tukey post hoc comparison test. The criterion for statistical significance was considered .

3. Results

Experiment 1
In the morphine group, the time latency for entering the dark compartment was lower than that of the control group (Figure 1, ). The treatment of the animals by 150 and 450 mg/kg of saffron extract significantly increased the time latency for entering the dark compartment Twenty-four and forty-eight h after receiving a shock (Figure 1, and ). Administration of 50 mg/kg of saffron extract was not effective for changing the time latency for entering the dark compartment. The results also showed that the total time spent in the dark compartment by the animals of the morphine group was higher than that of the saline group (Figure 2, ). Twenty-four and forty-eight h after receiving the shock, the total time spent in the dark compartment by the animals of the pretrain 150 group was lower than that of the morphine group (Figure 2, both ). The results also indicated that the total time spent in the light compartment by the animals of the morphine group was lower than that of the saline group at 24 and 48 h after receiving the shock (Figure 3, and ). In the pretrain 150 group, the total time spent in the light compartment was higher than that of the morphine group at 48 h after receiving the shock (Figure 3, ).

494367.fig.001
Figure 1: The effects of pretraining injection of saffron extract on time latency for entering the dark compartment 24 and 48 h after receiving the shock in the experimental groups. The animals of control group received saline instead of both saffron extract and morphine. The animals of morphine group were treated by saline instead of SE but received morphine (5 mg/kg, s.c.) 30 min before the training phase. Pretrain 50, pretrain 150, and pretrain 450 groups were treated by 50, 150, and 450 mg/kg of SE (i.p.), respectively, for 3 days before the training phase. The data were presented as mean ± SEM of the time latency (8 animals in each group). ** compared with the control group; + and ++ compared with the morphine group.
494367.fig.002
Figure 2: The effects of pretraining injection of saffron extract on the time spent in the dark compartment 24 and 48 h after receiving the shock. The animals of control group received saline instead of both saffron extract and morphine. The animals of morphine group were treated by saline instead of SE but received morphine (5 mg/kg, s.c.) 30 min before the training phase. Pretrain 50, Pretrain 150, and pretrain 450 groups were treated by 50, 150, and 450 mg/kg of saffron extract (i.p.), respectively, for 3 days before the training phase. The data were presented as mean ± SEM of the total time spent in the dark compartment (8 animals in each group). ** compared with the control group; ++ compared with the morphine group.
494367.fig.003
Figure 3: The effects of pretraining injection of saffron extract on the total time spent in the light compartment 24 and 48 h after receiving the shock between the groups. The animals of control group received saline instead of both saffron extract and morphine. The animals of morphine group were treated by saline instead of SE but received morphine (5 mg/kg, s.c.) 30 min before the training phase. Pretrain 50, pretrain 150, and pretrain 450 groups were treated by 50, 150, and 450 mg/kg of SE (i.p.), respectively, for 3 days before the training phase. The data were presented as mean ± SEM of the total time spent in the light compartment (8 animals in each group). * and ** compared to control; + compared to morphine group.

Experiment 2
Treatment of the animals by 150 and 450 mg/kg of saffron before retention phases (24 and 48 h after the shock) increased the time latency for entering the dark compartment (Figure 4, ). The total time spent in the dark compartment by the animals treated by 450 mg/kg of saffron extract was lower than that of the morphine group (Figure 5, and ). However, there was no significant difference in the total time spent in the light compartment between these groups (Figure 6).

494367.fig.004
Figure 4: The effects of pretest injection of saffron extract on time latency for entering the dark compartment. The animals of the control group received saline instead of both saffron extract and morphine. The animals of morphine group were treated by saline instead of SE but received morphine (5 mg/kg, s.c.) 30 min before the training phase. Pretest 150 and pretest 450 groups were treated by 150 and 450 mg/kg of SE (i.p.), respectively, before the recall phase. The data were presented as mean ± SEM of the time latency (8 animals in each group). ** compared with the control group and ++ compared with the morphine group.
494367.fig.005
Figure 5: Comparison of the total time spent in the dark compartment in the experimental groups. The animals of the control group received saline instead of both saffron extract and morphine. The animals of morphine group were treated by saline instead of SE but received morphine (5 mg/kg, s.c.) 30 min before the training phase. Pretest 150 and pretest 450 groups were treated by 150 and 450 mg/kg of SE (i.p.), respectively, before the recall phase. The data were presented as mean ± SEM of the total time spent in the dark compartment (8 animals in each group).  ** compared with the control; + and ++ compared with the morphine group.
494367.fig.006
Figure 6: Comparison of the total time spent in the light compartment 24 and 48 h after receiving the shock between the groups. The animals of the control group received saline instead of both saffron extract and morphine. The animals of morphine group were treated by saline instead of SE but received morphine (5 mg/kg, s.c.) 30 min before the training phase. Pretest 150 and pretest 450 groups were treated by 150 and 450 mg/kg of SE (i.p.), respectively, before the recall phase. The data were presented as mean ± SEM of the total time spent in the light compartment (8 animals in each group).

4. Discussion

The results of the present study showed that saffron extract attenuated memory impairment induced by morphine. The results were in agreement with the results of previous studies showing the beneficial effects of saffron on memory [5, 26, 27]. Haghighizad et al. also suggested the protective effect of the saffron extract against morphine-induced inhibition of spatial learning and memory in rats. The used doses were lower than that in the present study [28]. It has been recently found that the alcoholic extract of the pistils of Crocus sativus L. affects learning and memory in mice [27]. In another study, oral administration of 125–500 mg/kg of Crocus sativus extract alone had no effect on the learning behavior of mice in passive avoidance test but significantly improved ethanol-induced impairment of memory acquisition [27]. It has been also shown that treatment of animals by 50–200 mg/kg crocin alone had no effect but significantly improved ethanol-induced impairment of memory acquisition in mice [5]. Intracerebroventricular administration of crocin significantly prevented from ethanol-induced inhibition of hippocampal LTP in anaesthetized rats in vivo [26, 29]. The results of the present study also showed that Crocus sativus extract inhibited of the deleterious effect morphine on memory.

There is accumulating evidence that opiates modulate synaptic transmission and plasticity in the brain. Opiates have been shown to alter glutamatergic transmission [30], neurogenesis [31], dendritic stability [32], and long-term potentiation [3335]. The passive avoidance paradigm used in the present study depends upon both the amygdala and hippocampal systems [3638]. It has been also shown that both the amygdala and hippocampus are involved in the effects of opioids on memory [3941]. The exact mechanism(s) of morphine induced impairment of memory formation have not been completely elucidated [42]. The role of NMDA receptors in morphine state-dependent learning has been suggested [43, 44]. These receptors are also involved in post-training memory processing by the amygdala and hippocampus [45]. Furthermore, NMDA receptors may have a role in the effect of saffron or its constituents on memory [46, 47]. Moreover, the analgesic effect of saffron is attenuated by NMDA receptor antagonists [48]. It has been suggested that opioid-induced impairment of memory formation may be accompanied by a decreased activity level in nitric oxide/cyclic guanosine monophosphate (NO/cGMP) signaling pathway [16]. The interaction of saffron with nitric oxide has been also reported [49]. It has been shown that morphine-induced memory recall might be influenced by the central cholinergic activity [50]. Beneficial effects of saffron on memory in inhibited cholinergic system animal models [2, 51] may be another explanation for the effect of the extract on memory in the present study. The sedative- effects of as well as the protective effects in pentylenetetrazole (PTZ-) induced seizure in mice and rats may imply that saffron affects the GABAergic system [12, 27, 52] in which the latter has a role in memory impairment by the opioids [53, 54]. It is believed that saffron extract, crocetin or crocin, could be useful in the treatment of brain neurodegenerative disorders because of its powerful antioxidant activities [55]. Considering the possible role of oxidative damage in the deleterious effect of morphine [56], the antioxidant activity of the extract can be considered as another explanation for the beneficial effects of saffron on morphine-induced memory impairments [56, 57]. A functional interaction between dopamine and opioid system in memory storage processes has been suggested [58]. This mechanism may also have a role in the effect of saffron on memory impairment by opioids [59]. There are also other pieces of evidence which confirm the interaction of the opioid system with saffron or its constituents. It has been indicated that crocin produces a dose-dependent antinociceptive effect and also increases morphine-induced antinociception [60]. The analgesic effects of saffron ethanolic extract have been attributed to its effect on the opioid system [48]. Hosseinzadeh and Jahanian. also showed that the aqueous extracts in doses 80–320 mg/kg and ethanolic ones in doses 400–800 mg/kg attenuated morphine withdrawal signs induced by naloxone in mice [1]. It was also shown that injection of 100 mg/kg of Crocus sativus extract inhibited the acquisition and expression of morphine-induced conditioned place preference [61, 62]. In the present study, 50–450 mg/kg of the saffron extract inhibited morphine-induced memory impairment; however, it seems that the medium dose was more effective. The results of the present study added evidence for the effects of saffron on the brain opioid system.

In the present study, the chemical compound(s) for the beneficial effects of saffron was not indentified. The presence of crocin as a water-soluble carotenoid, as well as the monoterpene aldehyde and its glucosides including safranal and picrocrocin, and flavonoids including quercetin and kaempferol in saffron, has been well documented [63]. The beneficial effects of saffron on memory have been repeatedly attributed to crocin [7, 51, 55, 63]. Therefore, the results of present study may at least in part be due to this component. However, the memory enhancing effect as well as the protective effects of safranal on PTZ-induced seizure model may also be a good evidence for the interaction of safranal with GABAergic system [6, 12, 13]. It was also shown that safranal affects the extracellular levels of glutamate and aspartate in hippocampal tissues of kainic acid-treated rats [9]. On the other hand, the interaction of safranal with opioid system has been suggested [1, 62]. For example it has been shown that safranal affects morphine-induced conditioned place preference [62]. The injection of safranal to morphine-dependent animals also acted as an opioid antagonist and induced-morphine withdrawal like behaviors including jumping, seizure, diarrhea, ptosis, irritability, and wet-dog shake [1]. Therefore, it seems that this constituent may also have a role in the results of present study. The precise compound(s) and mechanism(s) responsible for the efficacy of saffron extract on memory impairments elicited by morphine still remain as an important issue and need to be clarified by further studies.

5. Conclusion

The results of the present study showed that the aqueous extract of Crocus sativus prevented from morphine induced memory deficits in mice. Further studies are needed to confirm this protective effect of Crocus sativus.

Acknowledgment

The authors would like to thank the Vice Presidency of Research, Mashhad University of Medical Sciences, for its financial supports.

References

  1. H. Hosseinzadeh and Z. Jahanian, “Effect of Crocus sativus L. (saffron) stigma and its constituents, crocin and safranal, on morphine withdrawal syndrome in mice,” Phytotherapy Research, vol. 24, no. 5, pp. 726–730, 2010. View at Publisher · View at Google Scholar · View at Scopus
  2. N. Pitsikas and N. Sakellaridis, “Crocus sativus L. extracts antagonize memory impairments in different behavioural tasks in the rat,” Behavioural Brain Research, vol. 173, no. 1, pp. 112–115, 2006. View at Publisher · View at Google Scholar · View at Scopus
  3. M. H. Boskabady, M. Ghasemzadeh Rahbardar, H. Nemati, and M. Esmaeilzadeh, “Inhibitory effect of Crocus sativus (saffron) on histamine (H1) receptors of guinea pig tracheal chains,” Pharmazie, vol. 65, no. 4, pp. 300–305, 2010. View at Publisher · View at Google Scholar · View at Scopus
  4. F. I. Abdullaev and J. J. Espinosa-Aguirre, “Biomedical properties of saffron and its potential use in cancer therapy and chemoprevention trials,” Cancer Detection and Prevention, vol. 28, no. 6, pp. 426–432, 2004. View at Publisher · View at Google Scholar · View at Scopus
  5. M. Sugiura, Y. Shoyama, H. Saito, et al., “Crocin improves the ethanol-induced impairment of learning behaviors of mice in passive avoidance tasks,” Proceedings of the Japan Academy B, vol. 71, no. 10, pp. 319–324, 1995.
  6. H. Hosseinzadeh and T. Ziaei, “Effects of Crocus sativus stigma extract and its constituents, crocin and safranal, on intact memory and scopolamine-induced learning deficits in rats performing the Morris water maze task,” Journal of Medicinal Plants, vol. 5, no. 19, pp. 40–60, 2006. View at Scopus
  7. K. Abe, M. Sugiura, Y. Shoyama, and H. Saito, “Crocin antagonizes ethanol inhibition of NMDA receptor-mediated responses in rat hippocampal neurons,” Brain Research, vol. 787, no. 1, pp. 132–138, 1998. View at Publisher · View at Google Scholar · View at Scopus
  8. H. Hosseinzadeh and H. R. Sadeghnia, “Safranal, a constituent of Crocus sativus (saffron), attenuated cerebral ischemia induced oxidative damage in rat hippocampus,” Journal of Pharmacy and Pharmaceutical Sciences, vol. 8, no. 3, pp. 394–399, 2005. View at Scopus
  9. H. Hosseinzadeh, H. R. Sadeghnia, and A. Rahimi, “Effect of safranal on extracellular hippocampal levels of glutamate and aspartate during kainic acid treatment in anesthetized rats,” Planta Medica, vol. 74, no. 12, pp. 1441–1445, 2008. View at Publisher · View at Google Scholar · View at Scopus
  10. S. Akhondzadeh, N. Tahmacebi-Pour, A. A. Noorbala et al., “Crocus sativus L. in the treatment of mild to moderate depression: a double-blind, randomized and placebo-controlled trial,” Phytotherapy Research, vol. 19, no. 2, pp. 148–151, 2005. View at Publisher · View at Google Scholar · View at Scopus
  11. H. Hosseinzadeh, V. Motamedshariaty, and F. Hadizadeh, “Antidepressant effect of kaempferol, a constituent of saffron (Crocus sativus) petal, in mice and rats,” Pharmacologyonline, vol. 2, pp. 367–370, 2007. View at Scopus
  12. H. Hosseinzadeh and H. R. Sadeghnia, “Protective effect of safranal on pentylenetetrazol-induced seizures in the rat: involvement of GABAergic and opioids systems,” Phytomedicine, vol. 14, no. 4, pp. 256–262, 2007. View at Publisher · View at Google Scholar · View at Scopus
  13. H. Hosseinzadeh and F. Talebzadeh, “Anticonvulsant evaluation of safranal and crocin from Crocus sativus in mice,” Fitoterapia, vol. 76, no. 7-8, pp. 722–724, 2005. View at Publisher · View at Google Scholar · View at Scopus
  14. H. Hosseinzadeh and N. B. Noraei, “Anxiolytic and hypnotic effect of Crocus sativus aqueous extract and its constituents, crocin and safranal, in mice,” Phytotherapy Research, vol. 23, no. 6, pp. 768–774, 2009. View at Publisher · View at Google Scholar · View at Scopus
  15. I. Izquierdo, M. A. M. R. De Almeida, and V. R. Emiliano, “Unlike β-endorphin, dynorphin1-13 does not cause retrograde amnesia for shuttle avoidance or inhibitory avoidance learning in rats,” Psychopharmacology, vol. 87, no. 2, pp. 216–218, 1985. View at Scopus
  16. S. Khavandgar, H. Homayoun, and M. R. Zarrindast, “The effect of L-NAME and L-arginine on impairment of memory formation and state-dependent learning induced by morphine in mice,” Psychopharmacology, vol. 167, no. 3, pp. 291–296, 2003. View at Scopus
  17. F. Motamedi, M. Ghasemi, F. Davoodi, and N. Naghdi, “Comparison of learning and memory in morphine dependent rats using different behavioral models,” Iranian Journal of Pharmaceutical Research, vol. 2, no. 4, pp. 225–230.
  18. A. L. Vaccarino, G. A. Olson, R. D. Olson, and A. J. Kastin, “Endogenous opiates: 1998,” Peptides, vol. 20, no. 12, pp. 1527–1574, 1999. View at Publisher · View at Google Scholar · View at Scopus
  19. K. Saadipour, A. Sarkaki, H. Alaei, M. Badavi, and F. Rahim, “Forced exercise improves passive avoidance memory in morphine-exposed rats,” Pakistan Journal of Biological Sciences, vol. 12, no. 17, pp. 1206–1211, 2009. View at Publisher · View at Google Scholar · View at Scopus
  20. H. Alaei, L. Borjeian, M. Azizi, S. Orian, A. Pourshanazari, and O. Hanninen, “Treadmill running reverses retention deficit induced by morphine,” European Journal of Pharmacology, vol. 536, no. 1-2, pp. 138–141, 2006. View at Publisher · View at Google Scholar · View at Scopus
  21. A. R. Ebrahimzadeh Bideskan, M. Hosseini, T. Mohammadpour et al., “Effects of soy extract on pentylenetetrazol-induced seizures in ovariectomized rats,” Journal of Chinese Integrative Medicine, vol. 9, no. 6, pp. 611–618, 2011. View at Publisher · View at Google Scholar · View at Scopus
  22. H. Rakhshandah and M. Hosseini, “Potentiation of pentobarbital hypnosis by Rosa damascena in mice,” Indian Journal of Experimental Biology, vol. 44, no. 11, pp. 910–912, 2006. View at Scopus
  23. M. Hosseini, M. G. Rahbardar, H. R. Sadeghnia, and H. Rakhshandeh, “Effects of different extracts of rosa damascena on pentylenetetrazol-induced seizures in mice,” Journal of Chinese Integrative Medicine, vol. 9, no. 10, pp. 1118–1124, 2011. View at Publisher · View at Google Scholar
  24. M. Nassiri-Asl, F. Zamansoltani, A. Javadi, and M. Ganjvar, “The effects of rutin on a passive avoidance test in rats,” Progress in Neuro-Psychopharmacology and Biological Psychiatry, vol. 34, no. 1, pp. 204–207, 2010. View at Publisher · View at Google Scholar · View at Scopus
  25. J. W. Wright, J. A. Clemens, J. A. Panetta et al., “Effects of LY231617 and angiotensin IV on ischemia-induced deficits in circular water maze and passive avoidance performance in rats,” Brain Research, vol. 717, no. 1-2, pp. 1–11, 1996. View at Publisher · View at Google Scholar · View at Scopus
  26. M. Sugiura, Y. Shoyama, H. Saito, and K. Abe, “Crocin (crocetin di-gentiobiose ester) prevents the inhibitory effect of ethanol on long-term potentiation in the dentate gyrus in vivo,” Journal of Pharmacology and Experimental Therapeutics, vol. 271, no. 2, pp. 703–707, 1994. View at Scopus
  27. Y. Zhang, Y. Shoyama, M. Sugiura, and H. Saito, “Effects of Crocus sativus L. on the ethanol-induced impairment of passive avoidance performances in mice,” Biological and Pharmaceutical Bulletin, vol. 17, no. 2, pp. 217–221, 1994. View at Scopus
  28. H. Haghighizad, A. Pourmotabbed, and H. Sahraei, “Protective effect of Saffron extract on morphine-induced inhibition of spatial learning and memory in rat,” Physiology and Pharmacology, vol. 12, no. 3, pp. 170–179, 2008.
  29. M. Sugiura, Y. Shoyama, H. Saito, and K. Abe, “Crocin (crocetin di-gentiobiose ester) prevents the inhibitory effect of ethanol on long-term potentiation in the dentate gyrus in vivo,” Journal of Pharmacology and Experimental Therapeutics, vol. 271, no. 2, pp. 703–707, 1994. View at Scopus
  30. N. J. Xu, L. Bao, H. P. Fan et al., “Morphine withdrawal increases glutamate uptake and surface expression of glutamate transporter GLT1 at hippocampal synapses,” Journal of Neuroscience, vol. 23, no. 11, pp. 4775–4784, 2003. View at Scopus
  31. A. J. Eisch, M. Barrot, C. A. Schad, D. W. Self, and E. J. Nestler, “Opiates inhibit neurogenesis in the adult rat hippocampus,” Proceedings of the National Academy of Sciences of the United States of America, vol. 97, no. 13, pp. 7579–7584, 2000. View at Publisher · View at Google Scholar · View at Scopus
  32. D. Liao, H. Lin, Y. L. Ping, and H. H. Loh, “Mu-opioid receptors modulate the stability of dendritic spines,” Proceedings of the National Academy of Sciences of the United States of America, vol. 102, no. 5, pp. 1725–1730, 2005. View at Publisher · View at Google Scholar
  33. F. A. Mansouri, F. Motamedi, Y. Fathollahi, N. Atapour, and S. Semnanian, “Augmentation of LTP induced by primed-bursts tetanic stimulation in hippocampal CA1 area of morphine dependent rats,” Brain Research, vol. 769, no. 1, pp. 119–124, 1997. View at Publisher · View at Google Scholar · View at Scopus
  34. F. A. Mansouri, F. Motamedi, and Y. Fathollahi, “Chronic in vivo morphine administration facilitates primed-bursts- induced long-term potentiation of Schaffer collateral-CA1 synapses in hippocampal slices in vitro,” Brain Research, vol. 815, no. 2, pp. 419–423, 1999. View at Publisher · View at Google Scholar · View at Scopus
  35. L. Pu, G. B. Bao, N. J. Xu, L. Ma, and G. Pei, “Hippocampal long-term potentiation is reduced by chronic opiate treatment and can be restored by re-exposure to opiates,” Journal of Neuroscience, vol. 22, no. 5, pp. 1914–1921, 2002. View at Scopus
  36. L. Stubley-Weatherly, J. W. Harding, and J. W. Wright, “Effects of discrete kainic acid-induced hippocampal lesions on spatial and contextual learning and memory in rats,” Brain Research, vol. 716, no. 1-2, pp. 29–38, 1996. View at Publisher · View at Google Scholar · View at Scopus
  37. M. Sakurai, M. Sekiguchi, K. Zushida et al., “Reduction in memory in passive avoidance learning, exploratory behaviour and synaptic plasticity in mice with a spontaneous deletion in the ubiquitin C-terminal hydrolase L1 gene,” European Journal of Neuroscience, vol. 27, no. 3, pp. 691–701, 2008. View at Publisher · View at Google Scholar · View at Scopus
  38. R. J. McDonald and N. M. White, “A triple dissociation of memory systems: hippocampus, amygdala, and dorsal striatum,” Behavioral Neuroscience, vol. 107, no. 1, pp. 3–22, 1993. View at Publisher · View at Google Scholar · View at Scopus
  39. H. Miladi-Gorji, A. Rashidy-Pour, Y. Fathollahi, M. M. Akhavan, S. Semnanian, and M. Safari, “Voluntary exercise ameliorates cognitive deficits in morphine dependent rats: the role of hippocampal brain-derived neurotrophic factor,” Neurobiology of Learning and Memory, vol. 96, no. 3, pp. 479–491, 2011. View at Publisher · View at Google Scholar
  40. M. Gallagher and B. S. Kapp, “Manipulation of opiate activity in the amygdala alters memory processes,” Life Sciences, vol. 23, no. 19, pp. 1973–1977, 1978. View at Scopus
  41. M. R. Zarrindast, F. Asadi, and A. Rezayof, “Repeated pretreatment of morphine prevents morphine-induced amnesia: a possible involvement for dorsal hippocampal NMDA receptors,” Archives of Iranian Medicine, vol. 14, no. 1, pp. 32–38, 2011. View at Scopus
  42. L. A. Bruins Slot and F. C. Colpaert, “Opiate states of memory: receptor mechanisms,” Journal of Neuroscience, vol. 19, no. 23, pp. 10520–10529, 1999. View at Scopus
  43. M. R. Zarrindast, M. Jafari-Sabet, M. Rezayat, B. Djahanguiri, and A. Rezayof, “Involvement of NMDA receptors in morphine state-dependent learning in mice,” International Journal of Neuroscience, vol. 116, no. 6, pp. 731–743, 2006. View at Publisher · View at Google Scholar · View at Scopus
  44. V. Cestari and C. Castellano, “MK-801 potentiates morphine-induced impairment of memory consolidation in mice: involvement of dopaminergic mechanisms,” Psychopharmacology, vol. 133, no. 1, pp. 1–6, 1997. View at Publisher · View at Google Scholar · View at Scopus
  45. I. Izquierdo, C. Da Cunha, R. Rosat, D. Jerusalinsky, M. B. C. Ferreira, and J. H. Medina, “Neurotransmitter receptors involved in post-training memory processing by the amygdala, medial septum, and hippocampus of the rat,” Behavioral and Neural Biology, vol. 58, no. 1, pp. 16–26, 1992. View at Publisher · View at Google Scholar · View at Scopus
  46. M. Lechtenberg, D. Schepmann, M. Niehues, N. Hellenbrand, B. Wünsch, and A. Hensel, “Quality and functionality of saffron: quality control, species assortment and affinity of extract and isolated saffron compounds to NMDA and σ1 (Sigma-1) receptors,” Planta Medica, vol. 74, no. 7, pp. 764–772, 2008. View at Publisher · View at Google Scholar
  47. K. Abe, M. Sugiura, S. Yamaguchi, Y. Shoyama, and H. Saito, “Saffron extract prevents acetaldehyde-induced inhibition of long-term potentiation in the rat dentate gyrus in vivo,” Brain Research, vol. 851, no. 1-2, pp. 287–289, 1999. View at Publisher · View at Google Scholar · View at Scopus
  48. S. Nasri, H. Sahraei, and H. Zardooz, “Inhibition of pain and inflamation induced by formalin in male mice by ethanolic extract of saffron (Crocus sativus) and its constituents crocin and safranal,” Kowsar Medical Journal, vol. 15, no. 4, pp. 189–195, 2011.
  49. F. Nabavizadeh, E. Salimi, Z. Sadroleslami, S. M. Karimian, and J. Vahedian, “Saffron (Crocus sativus) increases gastric acid and pepsin secretions in rats: role of nitric oxide (NO),” African Journal of Pharmacy and Pharmacology, vol. 3, no. 5, pp. 181–184, 2009. View at Scopus
  50. M. R. Jafari, M. R. Zarrindast, and B. Djahanguiri, “Influence of cholinergic system modulators on morphine state-dependent memory of passive avoidance in mice,” Physiology and Behavior, vol. 5, supplement, article S163, 2006. View at Publisher · View at Google Scholar
  51. M. R. Ghadami and A. Pourmotabbed, “The effect of crocin on scopolamine induced spatial learning and memory deficits in rats,” Physiology and Pharmacology, vol. 12, no. 4, pp. 287–295, 2009. View at Scopus
  52. N. Pitsikas, A. Boultadakis, G. Georgiadou, P. A. Tarantilis, and N. Sakellaridis, “Effects of the active constituents of Crocus sativus L., crocins, in an animal model of anxiety,” Phytomedicine, vol. 15, no. 12, pp. 1135–1139, 2008. View at Publisher · View at Google Scholar · View at Scopus
  53. J. D. Brioni, A. H. Nagahara, and J. L. McGaugh, “Involvement of the amygdala GABAergic system in the modulation of memory storage,” Brain Research, vol. 487, no. 1, pp. 105–112, 1989. View at Scopus
  54. M. R. Zarrindast, M. Noorbakhshnia, F. Motamedi, A. Haeri-Rohani, and A. Rezayof, “Effect of the GABAergic system on memory formation and state-dependent learning induced by morphine in rats,” Pharmacology, vol. 76, no. 2, pp. 93–100, 2006. View at Publisher · View at Google Scholar · View at Scopus
  55. K. Abe and H. Saito, “Effects of saffron extract and its constituent crocin on learning behaviour and long-term potentiation,” Phytotherapy Research, vol. 14, no. 3, pp. 149–152, 2000.
  56. D. C. Guzmán, I. E. Vázquez, N. O. Brizuela et al., “Assessment of oxidative damage induced by acute doses of morphine sulfate in postnatal and adult rat brain,” Neurochemical Research, vol. 31, no. 4, pp. 549–554, 2006. View at Publisher · View at Google Scholar · View at Scopus
  57. M. A. Papandreou, M. Tsachaki, S. Efthimiopoulos, P. Cordopatis, F. N. Lamari, and M. Margarity, “Memory enhancing effects of saffron in aged mice are correlated with antioxidant protection,” Behavioural Brain Research, vol. 219, no. 2, pp. 197–204, 2011. View at Publisher · View at Google Scholar · View at Scopus
  58. C. Castellano, V. Cestari, S. Cabib, and S. Puglisi-Allegra, “The effects of morphine on memory consolidation in mice involve both D1 and D2 dopamine receptors,” Behavioral and Neural Biology, vol. 61, no. 2, pp. 156–161, 1994. View at Scopus
  59. P. S. Widdowson and R. B. Holman, “Ethanol-induced increase in endogenous dopamine release may involve endogenous opiates,” Journal of Neurochemistry, vol. 59, no. 1, pp. 157–163, 1992. View at Publisher · View at Google Scholar · View at Scopus
  60. E. Tamaddonfard and N. Hamzeh-Gooshchi, “Effect of crocin on the morphine-induced antinociception in the formalin test in rats,” Phytotherapy Research, vol. 24, no. 3, pp. 410–413, 2010. View at Publisher · View at Google Scholar · View at Scopus
  61. N. Mojabi, A. Eidi, M. Kamalinejad, et al., “Study of the effects of intra-nucleus accumbens shell injections of alcohlic extract of Crocus sativus on the acquisition and expression of morphine-induced conditioned place preference in rats,” Physiology and Pharmacology, vol. 12, no. 2, pp. 121–128, 2008.
  62. H. Sahraei, M. Mohammadi, M. Kamalinejad, J. Shams, H. Ghoshooni, and A. Noroozzadeh, “Effects of the Crocus sativus L. extract on the acquisition and expression of morphine-induced conditioned place preference in female mice,” Journal of Medicinal Plants, vol. 7, no. 25, pp. 29–38, 2008.
  63. H. Hosseinzadeh, H. R. Sadeghnia, F. A. Ghaeni, V. S. Motamedshariaty, and S. A. Mohajeri, “Effects of saffron (Crocus sativus L.) and its active constituent, crocin, on recognition and spatial memory after chronic cerebral hypoperfusion in rats,” Phytotherapy Research, vol. 26, no. 3, pp. 381–386, 2012. View at Publisher · View at Google Scholar · View at Scopus