Systemic corticosterone enhances fear memory extinction in rats: Involvement of the infralimbic medial prefrontal cortex GABAA and GABAB receptors.

PURPOSE: The infralimbic (IL) subregion of the medial prefrontal cortex (mPFC) regulates the extinction of conditioned fear memory. Glucocorticoid and gamma-aminobutyric acid (GABA) receptors are expressed in the mPFC and are also critical in fear extinction. This study investigated the possible interactive effects of the glucocorticoids and GABAergic system in the IL on the regulation of fear extinction. METHOD: The rats were trained using an auditory fear conditioning task during which they received three conditioned stimuli (tones, 30 s, 4 kHz, 80 dB), co-terminated with the three unconditioned stimuli (footshock, 0.8 mA, 1 s). Extinction testing was conducted over 3 days (Ext 1-3). Thirty minutes before the first extinction trial (Ext 1), the rats received bicuculline (BIC, 1 mg/kg/2 mL, intraperitoneal [i.p.]) as a GABAA receptor antagonist or CGP55845 (CGP, 0.1 mg/kg/2 ML, i.p.) as a GABAB receptor antagonist followed by systemic injection of corticosterone (CORT, 3 mg/kg/2 ML, i.p.). Furthermore, separate groups of rats received a bilateral intra-IL injection of BIC (100 ng/0.3 µL/side) or CGP (10 ng/0.3 µL/side) followed by a systemic injection of CORT (3 mg/kg/2 ML, i.p.) before the first extinction trial (Ext 1). The extracellular signal-regulated kinase (ERK1) and cAMP response element-binding (CREB) activity in the IL was examined by Western blot analysis after Ext 1. FINDING: The results indicated that systemic CORT injection facilitated fear extinction and increased the expression of ERK1 but not CREB in the IL. Both systemic and intra-IL co-injection of BIC or CGP blocked the effects of CORT on fear extinction and ERK1 expression. CONCLUSION: These findings suggest that glucocorticoids and the GABAergic system may modulate fear extinction through the ERK pathway in the IL.

Saffron and crocin ameliorate prenatal valproic acid-induced autistic-like behaviors and brain oxidative stress in the male offspring rats.

Autism is a neurobehavioral disease that induces cognitive and behavioral alterations, usually accompanied by oxidative stress in the brain. Crocus sativus (saffron) and its active ingredient, crocin, have potent antioxidative effects that may benefit autistic behaviors. This study aimed to determine the effects of saffron extract and crocin against brain oxidative stress and behavioral, motor, and cognitive deficits in an animal model of autism in male offspring rats. 14 female rats were randomly divided into the saline and valproic acid (VPA) groups. Then, they were placed with mature male rats to mate and produce offspring. VPA (500 mg/kg, i.p.) was injected on day 12.5 of pregnancy (gestational day, GD 12.5) to induce an experimental model of autism. 48 male pups were left undisturbed for 29 days. First-round behavioral tests (before treatments) were performed on 30-33 post-natal days (PND), followed by 28 days of treatment (PND 34-61) with saffron (30 mg/kg, IP), crocin (15 or 30 mg/kg, i.p.), or saline (2 ml/kg, i.p.). The second round of behavioral tests (after treatments) was performed on PND 62-65 to assess the effects of the treatments on behavioral and cognitive features. In the end, animals were sacrificed under deep anesthesia, and their brains were dissected to evaluate the brain oxidative stress parameters, including malondialdehyde (MDA), glutathione (GSH), and catalase (CAT). VPA injection into female rats increased anxiety-like behaviors, enhanced pain threshold, impaired motor functions, disturbed balance power, increased MDA, and decreased GSH and CAT in their male offspring. 28 days of treatment with saffron or crocin significantly ameliorated behavioral abnormalities, reduced MDA, and increased GSH and CAT levels. Brain oxidative stress has been implicated in the pathophysiology of autistic-like behaviors. Saffron and crocin ameliorate anxiety-like behaviors, pain responses, motor functions, and brain oxidative stress parameters in an experimental model of autism. Saffron and crocin may hold promise as herbal-based pharmacological treatments for individuals with autism. However, further histological evidence is needed to confirm their efficacy.

Corticosterone injection into the infralimbic prefrontal cortex enhances fear memory extinction: Involvement of GABA receptors and the extracellular signal-regulated kinase.

This study investigated the interactive effect of glucocorticoid and Gamma-aminobutyric acid (GABA) receptors in the Infralimbic (IL) cortex on fear extinction in rats' auditory fear conditioning task (AFC). Animals received 3 conditioning trial tones (conditioned stimulus, 30 s, 4 kHz, 80 dB) co-terminated with a footshock (unconditioned stimulus, 0.8 mA, 1 s). Extinction testing was conducted over 3 days (Ext 1-3) after conditioning. Intra-IL injection of corticosterone (CORT, 20 ng/0.3 µl/side) was performed 15 min before the first extinction trial (Ext 1) which attenuated auditory fear expression in subsequent extinction trials (Ext 1-3), demonstrating fear memory extinction enhancement. Co-injection of the GABAA agonist muscimol (250 ng/0.3 µl/side) or the GABAB agonist baclofen (250 ng/0.3 µl/side) 15 min before corticosterone, did not significantly affect the facilitative effects of corticosterone on fear extinction. However, co-injection of the GABAA antagonist bicuculline (BIC, 100 ng/0.3 µl/side) or the GABAB antagonist CGP35348 (CGP, 100 ng/0.3 µl/side) 15 min before corticosterone, blocked the facilitative effects of corticosterone on fear extinction. Moreover, extracellular signal-regulated kinase (ERK) and cAMP response element-binding (CREB) in the IL were examined by Western blotting analysis after the first extinction trial (Ext 1) in some groups. Intra-IL injection of corticosterone increased the ERK activity but not CREB. Co-injection of the bicuculline or CGP35348 blocked the enhancing effect of corticosterone on ERK expression in the IL. Glucocorticoid receptors (GRs) activation in the IL cortex by corticosterone increased ERK activity and facilitated fear extinction. GABAA or GABAB antagonists decreased ERK activity and inhibited corticosterone's effect. GRs and GABA receptors in the IL cortex jointly modulate the fear extinction processes via the ERK pathway. This pre-clinical animal study may highlight GRs and GABA interactions in the IL cortex modulating fear memory processes in fear-related disorders such as post-traumatic stress disorder (PTSD).

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.

Beneficial effects of Spirogyra Neglecta Extract on antioxidant and anti-inflammatory factors in streptozotocin-induced diabetic rats.

Objectives This study was conducted to evaluate the effects of oral supplementation of Spirogyra algae on oxidative damages and inflammatory responses in streptozotocin (STZ)-induced diabetic rats. Methods Diabetes was induced by administration of 55 mg/kg of streptozotocin. A total of sixty-four rats were divided into eight groups of eight rats each as follows:1) non-diabetic control; 2, 3, and 4) non-diabetic rats treated with 15, 30, and 45 mg of Spirogyra algae/kg/d; 5) control diabetic; and 6, 7, and 8) diabetic rats treated with 15, 30, and 45 mg of Spirogyra algae extract. At the end of the trial, the serum concentrations of glucose, interleukin-6 (IL-6), tumor necrosis factor-a (TNF-a), malondialdehyde (MDA), glutathione (GSH), total antioxidant status (TAS), C-reactive protein (CRP), insulin, triglycerides, and cholesterol were examined by specified procedures. Results Our findings indicated that the administration of STZ significantly increased the serum concentrations of glucose, triglycerides, cholesterol, CRP, IL-6, TNF-a, and MDA and decreased the serum levels of GSH and TAS (P<0.05) in diabetic rats. Oral administration of Spirogyra alleviated adverse effects of diabetes on oxidative stress and inflammatory factors in diabetic rats (P<0.05). Conclusion It can be stated that Spirogyra algae extract can be used for treatment of diabetes likely due to prevention of oxidative stress and alleviation of inflammation in the rat model.