Saffron (Crocus sativus L.) stigma reduces symptoms of morphine-induced dependence and spontaneous withdrawal in rats.

Background: Chronic morphine induces physical and psychological dependence signs. Saffron (Crocus sativus L.) stigma has been shown to have anxiolytic, antidepressant, and antinociceptive properties and to alleviate naloxone-precipitated withdrawal signs.Objectives: Therefore, this study was designed to examine the effects of saffron aqueous extract on the severity of physical-psychological dependence, voluntary morphine consumption, and the cerebrospinal fluid (CSF) serotonin levels following locomotor sensitization in morphine-dependent rats and in rats undergoing morphine withdrawal.Materials: Adult male rats were treated with morphine (10 mg/kg, sc twice daily) for 10 days. Rats received saffron extract (60 mg/kg, ip) daily, during the induction of morphine dependence and/or withdrawal. Then, rats were tested for spontaneous withdrawal signs, anxiety using the elevated plus-maze, depression using sucrose preference test, and voluntary morphine consumption using a two-bottle choice paradigm, and then challenged with morphine (1 mg/kg, ip) to evaluate of locomotor sensitization and CSF serotonin levels.Results: The results showed saffron extract during induction of morphine dependence decreased the severity of withdrawal signs (P = .05), while it had no effect on anxiety and depression-like behaviors. Saffron extract during morphine withdrawal exhibited an increase in the percentage (or ratio) of open/total arm entries (P = .017), higher levels of sucrose preference (P = .0001), a lower morphine preference ratio (P = .02) and also, a decrease in locomotor activity (P = .004) and an increase in the CSF serotonin levels (P = .041) in rats challenged to morphine.Conclusions: Saffron extract may exert a protective effect against morphine-induced behavioral sensitization in rats, probably through increasing serotonin levels.

Role of Muscarinic Receptors in Hypoalgesia Induced by Crocin in Neuropathic Pain Rats.

OBJECTIVE: Crocin as an important constituent of saffron has antineuropathic pain properties; however, the exact mechanism of this effect is not known. The aim of this study was whether the hypoalgesic effect of crocin can be exerted through muscarinic receptors. MATERIALS AND METHODS: In the present project, 36 male Wistar rats (200 ± 20 g) were used. Animals randomly divided into six groups (sham, neuropathy, neuropathy + crocin, neuropathy + atropine 0.5 mg/kg, neuropathy + atropine 1 mg/kg, and neuropathy + atropine 1 mg/kg + crocin). Neuropathy was induced by the chronic constriction injury (CCI) method on the sciatic nerve. Crocin and atropine was administered intraperitoneally during 14 days following the 14th day after surgery. Pain response was detected every three days, two hours after each injection and 3 days following last injection. Mechanical allodynia and thermal hyperalgesia were detected using the Von Frey filaments and plantar test device, respectively. RESULTS: CCI significantly reduced the paw withdrawal response to mechanical and thermal stimulus (P < 0.01 and P < 0.05, respectively). Crocin therapy significantly reduced mechanical allodynia and thermal hyperalgesia induced by CCI (P < 0.05). Atropine pretreatment significantly blocked the hypoalgesic effect of crocin (P < 0.05 in mechanical allodynia and P < 0.01 in thermal hyperalgesia). Fourteen days administration of atropine alone at a dose of 0.5 mg/kg but not 1 mg/kg significantly reduced CCI-induced mechanical allodynia at day 30 after surgery. CONCLUSION: Crocin significantly decreased CCI-induced neuropathic pain. The hypoalgesic effect of crocin was blocked by atropine pretreatment, which indicates an important role for muscarinic receptors in the effect of crocin.

Role of Cannabinoid Receptors in Crocin-Induced Hypoalgesia in Neuropathic Pain in Rats.

PURPOSE: Neuropathic pain involves injury or alteration of the normal sensory and modulatory nervous systems to produce a set of symptoms that are often difficult to treat. Previous study indicates that crocin has anti-inflammatory properties that may be mediated by the neurotransmitter system. In this study, we determine if there is an interaction between crocin and the cannabinoid system on chronic constriction injury (CCI)-induced neuropathic pain in male rats. MATERIALS AND METHODS: In this experimental study, adult male Wistar rats (220-250 g) were used. CCI was induced by setting four loose ligatures around the sciatic nerve. In part 1, after nerve lesion, vehicle, crocin (60 mg/kg) or Win 55-212-2 (0.1 mg/kg) as an agonist and AM 251 (0.1 mg/kg) as an antagonist of cannabinoid receptors were injected intraperitoneally daily in separate groups for 2 weeks. In part 2, two weeks after nerve lesion, vehicle (5 µL), crocin (6 µg/5 µL), Win 55-212-2 (0.1 µg/5 µL), AM 251 (0.1 µg/5 µL) were administered intracerebroventricularly (ICV) in separate groups. Mechanical allodynia and thermal hyperalgesia were measured using Von Frey filaments and plantar test device, respectively, at day 14. Data were analyzed by two-way ANOVA and Sidak's multiple comparisons post-test. RESULTS: Results indicated that centrally administered crocin significantly decreased thermal hyperalgesia and mechanical allodynia. Also, peripheral injection of crocin significantly decreased mechanical allodynia but not thermal hyperalgesia. Central or peripheral administration of Win 55-212-2 or AM 251 modulates the analgesic effect of crocin significantly. CONCLUSION: Our findings showed that crocin has significant analgesic effects that are probably mediated by an endocannabinoid mechanism.

Effect of crocin on morphine tolerance and serum BDNF levels in a rat model of neuropathic pain.

BACKGROUND: Chronic use of morphine treatment for neuropathic pain leads to morphine-induced analgesic tolerance. Crocin contained in Crocus sativus L., exerts anti-inflammatory and analgesic effects. This study examined the effects of crocin on morphine tolerance and serum BDNF levels on neuropathic pain induced by chronic constriction injury (CCI) in rats. METHODS: CCI model of neuropathic pain was done in male Wistar rats (200-250 g). Rats were treated with crocin (15 or 30 mg/kg, intraperitoneally) alone or simultaneously with morphine (10 mg/kg, subcutaneously) during or after induction of CCI. Pain behavioral responses including mechanical allodynia and thermal hyperalgesia were measured from days of 15-27 after CCI. Then, rats were evaluated for serum BDNF levels on days 14 and/or 27. RESULTS: We found that morphine tolerance developed after the induction of neuropathic pain. The injection of crocin (15 and 30 mg/kg) was able to enhance analgesic effect of morphine by reduction of mechanical allodynia on days 15-27 post-surgery in CCI rats. While preemptive administration of crocin at a lower dose (15 mg/kg) maintained the analgesic effect of morphine. Morphine injection and/or co-administration with crocin (15, 30 mg/kg) decreased serum BDNF levels in CCI rats. CONCLUSION: These findings indicate that crocin may have a therapeutic effect to maintain morphine analgesic efficacy and also to prevent the development of morphine tolerance in neuropathic pain, but probably not through BDNF.

Forced exercise attenuates neuropathic pain in chronic constriction injury of male rat: an investigation of oxidative stress and inflammation.

BACKGROUND AND OBJECTIVE: Initial peripheral/central nerve injuries, such as chronic constriction injury (CCI)/spinal cord injury, are often compounded by secondary mechanisms, including inflammation and oxidative stress, which may lead to chronic neuropathic pain characterized by hyperalgesia or allodynia. On the other hand, exercise as a behavioral and non-pharmacological treatment has been shown to alleviate chronic neuropathic pain. Therefore, this study was conducted to examine whether or not exercise reduces neuropathic pain through modifying oxidative stress and inflammation in chronic constriction injury of the sciatic nerve. MATERIALS AND METHODS: Wistar male rats weighing 200±20 g were randomly divided into five groups (normal, sham, CCI, pre-CCI exercise, and post-CCI exercise group). Sciatic nerve of anesthetized rats was loosely ligated to induce CCI, and they were then housed in separate cages. The rats ran on treadmill at a moderate speed for 3 weeks. Mechanical allodynia and thermal hyperalgesia were determined using von Frey filament and plantar test, respectively. Tumor necrosis factor-alpha (TNF-α) assayed in the cerebrospinal fluid, malondialdehyde, and total antioxidant capacity were measured in the serum using Western blot test, thiobarbituric acid, and ferric reducing ability of plasma (FRAP), respectively. RESULTS: The mechanical allodynia (P=0.024) and thermal hyperalgesia (P=0.002) in the CCI group were higher than those in the sham group. Exercise after CCI reduced (P=0.004) mechanical allodynia and thermal hyperalgesia (P=0.025) compared with the CCI group. Moreover, the level of FRAP in the CCI group was (P=0.001) lower than that in the sham group, and post-CCI exercise reversed FRAP amount toward the control level (P=0.019). The amount of malondialdehyde did not differ between groups. Level of TNF-α increased in the CCI group (P=0.0002) compared with sham group and post-CCI exercise could reverse it toward the level of control (P=0.005). CONCLUSION: Post CCI-exercise but not pre CCI-exercise reduces CCI-induced neuropathic pain. One of the possible involved mechanisms is increasing the total antioxidant capacity and reducing the amount of TNF-α.

Effects of Saffron (Crocus sativus L.) Stigma Extract and its Active Constituent Crocin on Neuropathic Pain Responses in a Rat Model of Chronic Constriction Injury.

This study was designed to investigate the therapeutic effects of saffron (Crocus sativus L.) and its main constituent crocin on neuropathic pain behavioral responses induced by chronic constriction injury (CCI) in rats. Adult male Wistar rats (200 to 250 g) were randomly assigned into 5 groups: Sham + saline, CCI + saline, CCI+ saffron (30 mg/kg), CCI + crocin (15 mg/kg) and CCI + crocin (30 mg/kg). CCI was induced by applying 4 loose ligatures around the sciatic nerve. Two weeks after nerve lesion, injections of saline, saffron or crocin were started and continued until 26(th) day post-surgery. Pain behavioral responses including mechanical allodynia (von Frey filament testing) and thermal hyperalgesia were measured in 14, 17, 20, 23, 26, and 40(th) days after CCI. CCI significantly increased pain behavioral responses. Saffron and crocin (30 mg/kg) decreased thermal hyperalgesia and mechanical allodynia on day 26, and this effect continued until the day 40. Crocin at lower dose (15 mg/kg) was ineffective. These findings indicate that treatment of saffron and crocin after CCI may have a therapeutic effect against neuropathic pain, suggesting that these substances may offer new strategies for the treatment of this highly debilitating condition.