Antidepressant effect and pharmacological evaluation of standardized extract of flavonoids from Byrsonima crassifolia

Byrsonima crassifolia (Malpighiaceae) has been used in traditional medicine for the treatment of some mental-related diseases; however, its specific neuropharmacological activities remain to be defined. The present study evaluates the anxiolytic, anticonvulsant, antidepressant, sedative effects produced by the extracts of Byrsonima crassifolia, and their influence on motor activity in ICR mice. Additionally, we determine the acute toxicity profiles of the Byrsonima crassifolia extracts and the presence of neuroactive constituents. Our results show that the methanolic extract of Byrsonima crassifolia produces a significant (P < 0.05) antidepressant effect in the forced swimming test in mice at 500 mg/kg dose. However, it does not possess anxiolytic, sedative, or anticonvulsant properties, and does not cause a reduction of mice locomotion (P > 0.05). Although the main compound of the methanolic extract was identified as quercetin 3-O-xyloside (12 mg/kg), our findings suggest that flavonoids, such as rutin (4.4 mg/kg), quercetin (1.4 mg/kg) and hesperidin (0.7 mg/kg), may be involved in the antidepressant effects. To the best of our knowledge, the present study constitutes the first report on the presence of the flavonoids with neuropharmacological activity rutin and hesperidin in Byrsonima crassifolia. In conclusion, the present results showed that the methanolic extract standardized on flavonoids content of Byrsonima crassifolia possesses potential antidepressant-like effects in the FST in mice, and could be considered as relatively safe toxicologically with no deaths of mice when orally administered at 2000 mg/kg.     

Chimeric peptide of Met-enkephalin and FMRFa induces antinociception and attenuates development of tolerance to morphine antinociception.

A synthetic chimeric peptide of Met-enkephalin and FMRFamide (YGGFMKKKFMRFa), based on MERF was synthesized. This peptide was tested for possible antinociceptive effects using the tail flick test in mice. The effect of the chimeric peptide on morphine antinociception and development of tolerance to the antinociceptive action of morphine was also investigated. The chimeric peptide produced significant, dose-dependent antinociception (40, 60 and 90 mg/kg) in the tail flick test. Pretreatment with naloxone (5 mg/kg, IP) significantly attenuated the antinociceptive effect induced by the chimeric peptide (90 mg/kg, IP), indicating involvement of an opioidergic mechanism. In combination experiments with morphine, the antinociceptive dose of the chimeric peptide (60 mg/kg, IP) potentiated morphine (7 mg/kg, IP) antinociception. A low dose of the chimeric peptide (10 mg/kg, IP), that did not produce significant antinociception on its own, also potentiated morphine antinociception. In the tolerance studies, male albino mice received twice daily injections of morphine (20 mg/kg, IP) followed by either saline (0.1 ml) or chimeric peptide (80 mg/kg, IP) for a period of 4 days. A control group received twice daily injections of saline (0.1 ml) for the same period. When tested on Day 5, tolerance to antinociceptive action of morphine (15 mg/kg, IP) was evidenced by decreased response in chronic morphine plus saline treated mice compared to control group. Concurrent administration of chimeric peptide (80 mg/kg, IP) with morphine significantly attenuated the development of tolerance to the antinociceptive action of morphine. The preliminary results of this study demonstrate that peripherally administered chimeric peptide can produce dose dependent, naloxone reversible, antinociception; potentiate morphine antinociception and attenuate morphine tolerance, indicating a possible role of these type of amphiactive sequences in antinociception and its modulation. These chimeric peptides may also prove to be useful tools for further ascertaining the role of FMRFa family of peptides in mechanisms leading to opiate tolerance and dependence.     

Involvement of nitric oxide (NO) signalling pathway in the antidepressant activity of essential oil of Valeriana wallichii Patchouli alcohol chemotype

Valeriana wallichii DC (Valerianaceae), popularly named as Indian valerian has been shown to exist as three chemotypes. The present study evaluated the antidepressant like effect of root essential oil of Valeriana wallichii patchouli alcohol chemotype in both acute and chronic treatment study using forced swim test (FST). Mice (n = 6 per group) received 10, 20 and 40 mg/kg p.o. doses of test drug. Single administration of oil significantly inhibited the immobility period (57.6% and 46.9%) at doses 20 and 40 mg/kg respectively without changing the motor function (p < 0.05). Similarly, daily administration of essential oil (20 mg/kg) for 14 days significantly reduced the immobility period (69.9%) in FST (p < 0.05). The neurotransmitter levels in mouse brain were estimated on day 14 after the behavioral study. Significant increase in the level of norepinephrine (29%) and serotonin (19%) (p < 0.05) was found at 20 mg/kg dose, while no change was observed at 10 and 40 mg/kg doses. The antidepressant-like effect of essential oil (20 mg/kg) was prevented by pretreatment of mice with l-arginine (750 mg/kg i.p.) and sildenafil (5 mg/kg i.p). On the contrary, pretreatment of mice with l-NAME (10 mg/kg i.p.) or methylene blue (10 mg/kg i.p.) potentiated the antidepressant action of essential oil (10 mg/kg). Taken together, these findings demonstrated that nitric oxide pathway is involved in mediating antidepressant like effect of essential oil from this chemotype.     

Role of KATP channels in reduced antinociceptive effect of morphine in streptozotocin-induced diabetic mice

The nociceptive effect was measured using withdrawal latency in tail flick test in mice rendered diabetic by administering streptozotocin (200 mg/kg, i.p.). The antinociceptive effect of morphine (4 and 8 mg/kg, s.c.) and cromakalim, a KATP channel opener, (0.3, 1 and 2 micrograms, i.c.v.) was significantly reduced in diabetic mice. Moreover, co-administration of cromakalim(0.3 microgram) did not alter the reduced antinociceptive effect of morphine(4 mg/kg) in diabetic mice. Spleenectomy in diabetic mice restored the decrease in antinociceptive effect of morphine and cromakalim. Multiple dose treatment with insulin to maintain euglycaemia for 3 days in diabetic mice prevented the decrease in antinociceptive effect of morphine and cromakalim. However, hyperglycaemic tyrode's buffer did not alter the pD2 value of morphine in isolated guinea pig ileum suggesting that hyperglycaemia does not interfere with mu receptor mediated responses in vitro. The results suggest that hyperglycaemia induced decrease in antinociceptive effect of morphine and cromakalim may be due to alteration in KATP channels. Some unknown factor from spleen in diabetic mice may be responsible for this alteration in KATP channels in diabetic mice.     

Bacopa monnieri modulates endogenous cytoplasmic and mitochondrial oxidative markers in prepubertal mice brain

Bacopa monnieri (BM) an herb, found throughout the Indian subcontinent in wet, damp and marshy areas is used in Ayurvedic system of medicine for improving intellect/memory, treatment of anxiety and neuropharmacological disorders. Although extensively given to children as a memory enhancer, no data exists on its ability to modulate neuronal oxidative stress in prepubertal animal models. Hence in this study, we examined if dietary intake of BM leaf powder has the propensity to modulate endogenous markers of oxidative stress, redox status (reduced GSH, thiol status), response of antioxidant defenses (enzymic), protein oxidation and cholinergic function in various brain regions of prepubertal (PP) mice. PP mice maintained on a BM-enriched diet (0.5 and 1%) for 4 weeks showed a significant diminution of basal oxidative markers (malondialdehyde levels, reactive species generation, hydroperoxide levels and protein carbonyls) in both cytoplasm and mitochondria of all brain regions. This was accompanied with enhanced reduced glutathione, thiol levels and elevated activities of antioxidant enzymes (catalase, glutathione peroxidase, superoxide dismutase). Significant reduction in the activity of acetyl cholinesterase enzyme in all brain regions suggested the potential of BM leaf powder to modulate cholinergic function. Further evidence that dietary intake of BM leaf powder confers the prepubertal brain with additional capacity to cope up with neurotoxic prooxidants was obtained by exposing cortical/cerebellar synaptosomes of normal and BM fed mice to 3-nitropropionic acid (3-NPA). While synaptosomes from control mice exhibited a concentration related lipid peroxidation and ROS generation, synaptosomes obtained from BM fed mice showed only a marginal induction at the highest concentration clearly suggesting their increased resistance to 3-NPA-induced oxidative stress. Collectively these data clearly indicate the potential of Bacopa monnieri to modulate endogenous markers of oxidative stress in brain tissue of PP mice. Based on these results, it is hypothesized that dietary intake of BM leaf powder confers neuroprotective advantage and is likely to be effective as a prophylactic/therapeutic agent for neurodegenerative disorders involving oxidative stress.     

Hypoglycemic effects of MDG-1, a polysaccharide derived from Ophiopogon japonicas, in the ob/ob mouse model of type 2 diabetes mellitus

Ophiopogon japonicus is a traditional Chinese medicine used to treat diabetes mellitus. We investigate the anti-ischemic properties of a water-soluble β-d-fructan (MDG-1) from O. japonicus, and assess the antidiabetic effects of MDG-1. In the study, ob/ob mice were treated with 150 mg/kg or 300 mg/kg MDG-1 by gavage for 23 d. Blood glucose levels were measured regularly. An oral glucose tolerance test (OGTT) was preformed on day 21. The levels of insulin, total cholesterol and triglyceride in the serum were measured at the end of administration. The liver triglyceride content and tissue weights were also determined. Results show that MDG-1 (300 mg/kg) was demonstrated to exert acute and long-term hypoglycemic effects on fed blood glucose in ob/ob mice. However, only a marginal hypoglycemic effect on fasting blood glucose levels was observed. MDG-1 (300 mg/kg) improved oral glucose tolerance and reduced serum insulin levels and triglyceride content in the liver in ob/ob mice. Furthermore, a reduction in body weight gain and the weight of subcutaneous fat were observed following treatment with MDG-1 (150 mg/kg) compared with the control group. MDG-1 had no significant effects on the total cholesterol and triglyceride levels, food intake and other adipose and organ tissues. These data suggest that MDG-1 exhibits hypoglycemic activity and reduces insulin resistance.     

Dietary pyridoxine enhances thermal tolerance of Labeo rohita (Hamilton) fingerlings reared under endosulfan stress

A preliminary experiment was carried out to study the effect of dietary pyridoxine (PN) on thermal tolerance of Labeo rohita fingerlings exposed to endosulfan (1/10th 96 h LC₅₀=0.2 ppb) stress, reared at 26.0±0.5 °C to assess its culture potential in different agro-climatic zones. Two hundred seventy fingerlings were randomly distributed into six treatment groups in triplicate. Five iso-caloric and iso-nitrogenous purified diets were prepared with graded levels of pyridoxine. Six treatment groups were T₀ (10 mg PN+without endosulfan), T₁ (0 mg PN+endosulfan), T₂ (10 mg PN+endosulfan), T₃ (50 mg PN+endosulfan), T₄ (100 mg PN+endosulfan) and T₅ (200 mg PN+endosulfan). After feeding for 60 days, critical temperature maxima (CTmax), lethal temperature maxima (LTmax), critical temperature minima (CTmin) and lethal temperature minima (LTmin) were determined in each group. There was significant (P<0.05) effect of dietary pyridoxine on temperature tolerance (CTmax, LTmax, CTmin and LTmin) of the groups fed diets supplemented with 100 and 200 mg PN/kg diet compared to other experimental groups. Positive correlations were observed between CTmax and LTmax (R²=0.85) as well as between CTmin and LTmin (R²=0.97). The effect was more prominent on lower thermal tolerance limit (CTmin and LTmin). The overall results obtained in this preliminary study indicated that pyridoxine supplementation at 100 mg PN/kg diet enhances the thermal tolerance of endosulfan exposed L. rohita fingerlings.     

Cariprazine (RGH-188), a potent D3/D2 dopamine receptor partial agonist, binds to dopamine D3 receptors in vivo and shows antipsychotic-like and procognitive effects in rodents

We investigated the in vivo effects of orally administered cariprazine (RGH-188; trans-N-{4-[2-[4-(2,3-dichlorophenyl)-piperazin-1-yl]-ethyl]-cyclohexyl}-N′,N′-dimethyl-urea), a D₃/D₂ dopamine receptor partial agonist with ∼10-fold preference for the D₃ receptor. Oral bioavailability of cariprazine at a dose of 1 mg/kg in rats was 52% with peak plasma concentrations of 91 ng/mL. Cariprazine 10 mg/kg had good blood-brain barrier penetration, with a brain/plasma AUC ratio of 7.6:1. In rats, cariprazine showed dose-dependent in vivo displacement of [³H](+)-PHNO, a dopamine D₃ receptor-preferring radiotracer, in the D₃ receptor-rich region of cerebellar lobules 9 and 10. Its potent inhibition of apomorphine-induced climbing in mice (ED₅₀ = 0.27 mg/kg) was sustained for 8 h. Cariprazine blocked amphetamine-induced hyperactivity (ED₅₀ = 0.12 mg/kg) and conditioned avoidance response (CAR) (ED₅₀ = 0.84 mg/kg) in rats, and inhibited the locomotor-stimulating effects of the noncompetitive NMDA antagonists MK-801 (ED₅₀ = 0.049 mg/kg) and phencyclidine (ED₅₀ = 0.09 mg/kg) in mice and rats, respectively. It reduced novelty-induced motor activity of mice (ED₅₀ = 0.11 mg/kg) and rats (ED₅₀ = 0.18 mg/kg) with a maximal effect of 70% in both species. Cariprazine produced no catalepsy in rats at up to 100-fold dose of its CAR inhibitory ED₅₀ value. Cariprazine 0.02-0.08 mg/kg significantly improved the learning performance of scopolamine-treated rats in a water-labyrinth learning paradigm. Though risperidone, olanzapine, and aripiprazole showed antipsychotic-like activity in many of these assays, they were less active against phencyclidine and more cataleptogenic than cariprazine, and had no significant effect in the learning task. The distinct in vivo profile of cariprazine may be due to its higher affinity and in vivo binding to D₃ receptors versus currently marketed typical and atypical antipsychotics.     

Antinociceptive,anti-inflammatory and antipyretic effects of 1.5-diphenyl-1H-Pyrazole-3-carbohydrazide,a new heterocyclic pyrazole derivative

Aims

Heterocyclic pyrazole derivative has been described for the treatment of pain and inflammatory diseases. This study evaluated the in vivo, antinociceptive, anti-inflammatory and antipyretic effects of 1.5-diphenyl-1H-Pyrazole-3-carbohydrazide (1.5-DHP) and the in vivo or in vitro mechanism of action.

Main methods

Acetic acid-induced writhing, hot-plate and formalin-induced nociception tests were used to evaluate the antinociceptive effect, while the rota-rod test was used to assess the motor activity. Croton oil-induced ear edema and carrageenan-induced peritonitis tests were used to investigate the anti-inflammatory effect of 1.5-DHP. The antipyretic effect was assessed using the LPS-induced fever model. The mechanism of action was evaluated by PGE₂ and TNF-α measurement and cyclooxygenase inhibition assay.

Key findings

Oral administration (p.o.) of 1.5-DHP (1, 3, 10 mg/kg) caused a dose-related inhibition of the acetic acid-induced writhing, however the highest dose was not effective on the hot-plate and rota-rod. In the formalin-induced nociception, 1.5-DHP (10 mg/kg, p.o.) inhibited only the late phase of nociception. This same dose of 1.5-DHP also reduced the croton oil-induced ear edema. 1.5-DHP (3, 10, 30 mg/kg, p.o.) produced a dose-related reduction of leukocyte migration on the carrageenan-induced peritonitis. 1.5-DHP (60 mg/kg, p.o.) reduced the fever and the increase of PGE₂ concentration in the cerebrospinal fluid induced by LPS. 1.5-DHP inhibited both COXs in vitro. Finally, 1.5-DHP (10 mg/kg, p.o.) reduced the TNF-α concentration in peritoneal exudates after carrageenan injection.

Significance

These results indicate that 1.5-DHP produces anti-inflammatory, antinociceptive and antipyretic effects by PGE₂ synthesis reduction through COX-1/COX-2 inhibition and by TNF-α synthesis/release inhibition.     

Seasonal variations in harvest index and bacoside A contents amongst accessions of <Emphasis Type="Italic">Bacopa monnieri</Emphasis> (L.) Wettst. collected from wild populations

Bacoside A, a major active principle of Bacopa monnieri known for its cognitive effects is a mixture of saponins like bacoside A3, bacopaside II, isomer of bacopasaponin C and bacopasaponin C. Seasonal changes in biomass and bacoside A levels in fourteen accessions of B. monnieri were evaluated after maintaining these at a common site at Thapar University campus, Patiala (30°19′36.12″N and 76°24′1.08″E) for 1 year. Harvestable biomass and total bacoside A contents varied significantly between the accessions and also in a particular accession during different seasons of the year. The maximum dry weight of plant (biomass 1.64 g) and bacoside A levels (6.82 mg/plant) were recorded in accession BM1. Harvestable biomass was highest during summer in accessions BM1 and BM7 (FW 4.2 g/plant), whereas bacoside A levels were also highest during summer and in accession BM1 (6.82 mg/plant). The lowest bacoside A level (0.06 mg/plant) was recorded in accession BM14 during winter. Principal component analysis showed that samples of summer were positively correlated with both the components suggesting an appropriate time for the harvest.     

Antidepressant-like Effect of Bacopaside I in Mice Exposed to Chronic Unpredictable Mild Stress by Modulating the Hypothalamic–Pituitary–Adrenal Axis Function and Activating BDNF Signaling Pathway

Preliminary studies conducted in our laboratory have confirmed that Bacopaside I (BS-I), a saponin compound isolated from Bacopa monnieri, displayed antidepressant-like activity in the mouse behavioral despair model. The present investigation aimed to verify the antidepressant-like action of BS-I using a mouse model of behavioral deficits induced by chronic unpredictable mild stress (CUMS) and further probe its underlying mechanism of action. Mice were exposed to CUMS for a period of 5 consecutive weeks to induce depression-like behavior. Then, oral gavage administrations with vehicle (model group), fluoxetine (12 mg/kg, positive group) or BS-I (5, 15, 45 mg/kg, treated group) once daily were started during the last two weeks of CUMS procedure. The results showed that BS-I significantly ameliorated CUMS-induced depression-like behaviors in mice, as characterized by an elevated sucrose consumption in the sucrose preference test and reduced immobility time without affecting spontaneous locomotor activity in the forced swimming test, tail suspension test and open field test. It was also found that BS-I treatment reversed the increased level of plasma corticosterone and decreased mRNA and protein expressions of glucocorticoid receptor induced by CUMS exposure, indicating that hypothalamic–pituitary–adrenal (HPA) axis hyperactivity of CUMS-exposed mice was restored by BS-I treatment. Furthermore, chronic administration of BS-I elevated expression levels of brain-derived neurotrophic factor (BDNF) (mRNA and protein) and activated the phosphorylation of extracellular signal-regulated kinase and cAMP response element-binding protein in the hippocampus and prefrontal cortex in mice subjected to CUMS procedure. Taken together, these results indicated that BS-I exhibited an obvious antidepressant-like effect in mouse model of CUMS-induced depression that was mediated, at least in part, by modulating HPA hyperactivity and activating BDNF signaling pathway.     

Toxoplasma gondii: Fluconazole and itraconazole activity against toxoplasmosis in a murine model

Toxoplasma gondii is an important opportunistic pathogen affecting immunocompromised patients with AIDS. Toxoplasmic encephalitis is responsible for high morbidity and mortality. In this study, we investigated the activity of the antifungals fluconazole (FLZ) and itraconazole (ITZ) against T. gondii in mice infected with the Me49 strain. As previously reported for ITZ, FLZ also demonstrated a selective effect against T. gondii in vitro; the IC₅₀ values obtained for FLZ were 8.9 μM and 3.1 μM after 24 h and 48 h of treatment, respectively. A 10-day treatment of mice with orally or intraperitoneally administered 20 mg/kg/day FLZ showed a significant survival difference compared to untreated mice. The administration of 20 mg/kg/day ITZ significantly reduced the brain cyst burden compared to untreated mice but did not exert significant protection against death. The results obtained in this work are rather promising as ITZ and FLZ are safe and low-cost drugs available on the market.     

Anti-fatigue activity of polysaccharides extract from Radix Rehmanniae Preparata

The anti-fatigue effects of the Radix Rehmanniae Preparata polysaccharides (RRPP) were studied in mice. The RRPP were orally administered at doses of 50, 100 and 200 mg/kg for 4 weeks and the anti-fatigue activity was evaluated using a weight-loaded swimming test, along with the determination of serum urea nitrogen (SUN), hepatic glycogen and blood lactic acid (BLA) contents. The results showed that there was no significant difference in the body weight of mice in the three RRPP groups compared with the negative control group during initial, intermediate and terminal stages in the experiment (p > 0.05). The ratio of exhausting swimming time was obviously increased 31.48% (p < 0.05) and 61.51% (p < 0.01) in the middle-dose group and the high-dose RRPP group, respectively. The BLA and SUN levels were decreased in middle-dose and high-dose RRPP groups (p < 0.01). Hepatic glycogen level was increased in three RRPP treated groups (p < 0.01). Therefore, RRPP may be responsible for the pharmacological effect of anti-fatigue of Radix Rehmanniae Preparata. The mechanism was related to the increase of the storage of hepatic glycogen and the decrease of the accumulation of SUN and BLA.     

Modulation of acute morphine tolerance by corticotropin-releasing factor and dynorphin A in the mouse spinal cord.

Previously, we have demonstrated that intrathecally (i.t.) administered corticotropin-releasing factor (CRF) in mice produces stimulus-specific antinociception and modulation of morphine-induced antinociception by mechanisms involving spinal kappa opioid receptors. Recently, we also have found that CRF releases immunoreactive dynorphin A, a putative endogenous kappa opioid receptor agonist, from superfused mice spinal cords in vitro. Dynorphin A administered intracerebroventricularlly (i.c.v.) to mice has been shown to modulate the expression of morphine tolerance. In the present study, the possible modulatory effects of i.t. administered CRF as well as dynorphin A on morphine tolerance were studied in an acute tolerance model. Subcutaneous administration of 100 mg/kg of morphine sulfate (MS) to mice caused an acute tolerance to morphine-induced antinociception. The antinociceptive ED50 of MS was increased from 4.4 mg/kg (naive mice) to 17.9 mg/kg (4 hours after the injection of 100 mg/kg MS). To study the modulatory effects of spinally administered CRF and dynorphin A on the expression of morphine tolerance, CRF and dynorphin A were injected i.t. at 15 min and 5 min, respectively, before testing the tolerant mice by the tail-flick assay. The antinociceptive ED50 of MS in tolerant mice was decreased to 8.8 mg/kg and 7.1 mg/kg, respectively, after i.t. administration of CRF (0.1 nmol) and dynorphin A (0.2 nmol). In contrast, 0.5 nmol of alpha-helical CRF (9-41), a CRF antagonist and 0.4 nmol of norbinaltorphimine, a highly selective kappa opioid receptor antagonist, when administered i.t. at 15 min before the tail-flick test in tolerant mice, increased the antinociceptive ED50 of MS to 56.6 mg/kg and 88.8 mg/kg, respectively. These data confirmed the modulatory effect of dynorphin A on morphine tolerance and suggested that CRF, which releases dynorphin A in several central nervous system regions, also plays a modulatory role in the expression of morphine tolerance.     

The involvement of midbrain astrocyte in the development of morphine tolerance

Aims

Systemic administration of opiate analgesics such as morphine remains the most effective treatment for alleviating severe pain across a range of conditions including acute pain. However, chronic or repeated administration of opiate analgesics results in the development of analgesic tolerance. Glial cells such as microglia and astrocytes are known to release various inflammatory cytokines and neurotrophic factors leading to regulation of neuronal function. Recently, glial cells were reported to play important roles in the development of analgesic tolerance to morphine. Here, we focused on the involvement of midbrain glial cells, particularly astrocytes, in the development of analgesic tolerance to morphine.

Main methods

Mice were treated with morphine (10 mg/kg, s.c.) or vehicle once a day for 5 days. Pentoxifylline (an inhibitor of glial activation; 20 mg/kg, i.p. or 50 and 100 μg/mouse, i.c.v.) was administered 30 min before morphine treatment. Flavopiridol (a cyclin-dependent kinase inhibitor; 5 nmol/mouse, i.c.v.) was administered 10 min before and 10 h after morphine treatment. The analgesic effect of morphine was measured using the tail flick method.

Key findings

The development of analgesic tolerance to morphine was gradually observed during daily treatment of morphine for 5 days in mice. On days 1 and 3 after repeated morphine treatment, astrocyte marker glial fibrillary acidic protein expression levels were significantly increased, as determined by western blot analyses. These phenomena were significantly inhibited following pre-treatment with pentoxifylline or flavopiridol.

Significance

We demonstrated that midbrain astrocytes play an important role in the development of analgesic tolerance to morphine.     

Analysis of the mechanisms underlying the antinociceptive effect of epicatechin in diabetic rats

Aims

The purpose of this study was to investigate the antinociceptive effect of epicatechin as well as the possible mechanisms of action in diabetic rats.

Main methods

Rats were injected with streptozotocin to produce hyperglycemia. The formalin test was used to assess the nociceptive activity.

Key findings

Acute pre-treatment with epicatechin (0.03–30 mg/kg, i.p.) prevented formalin-induced nociception in diabetic rats. Furthermore, daily or every other day treatment for 2 weeks with epicatechin (0.03–30 mg/kg, i.p.) also prevented formalin-induced nociception in diabetic rats. Acute epicatechin-induced antinociception was prevented by l-NAME (N^ω-nitro-l-arginine methyl ester hydrochloride, 1–10 mg/kg, non-selective nitric oxide synthesis inhibitor), 7-nitroindazole (0.1–1 mg/kg, selective neuronal nitric oxide synthesis inhibitor), ODQ (1H-(1,2,4)-oxadiazolo(4,2-a)quinoxalin-1-one, 0.2–2 mg/kg, guanylyl cyclase inhibitor) or glibenclamide (1–10 mg/kg, ATP-sensitive K⁺ channel blocker). Moreover, epicatechin (3 mg/kg)-induced antinociception was fully prevented by methiothepin (0.1–1 mg/kg, serotonergic receptor antagonist), WAY-100635 (0.03–0.3 mg/kg, selective 5-HT_1A receptor antagonist) or SB-224289 (0.03–0.3 mg/kg, selective 5-HT_1B receptor antagonist). In contrast, BRL-15572 (0.03–0.3 mg/kg, selective 5-HT_1D receptor antagonist) only slightly prevented the antinociceptive effect of epicatechin. Naloxone (0.1–1 mg/kg, opioid antagonist) did not modify epicatechin's effect.

Significance

Data suggest the involvement of the nitric oxide–cyclic GMP–K⁺ channel pathway as well as activation of 5-HT_1A and 5HT_1B, and at a lesser extent, 5-HT_1D, but not opioid, receptors in the antinociceptive effect of epicatechin in diabetic rats. Our data suggest that acute or chronic treatment with epicatechin may prove to be effective to treat nociceptive hypersensitivity in diabetic patients.     

Spilanthes acmella ethanolic flower extract: LC-MS alkylamide profiling and its effects on sexual behavior in male rats

According to Indian Systems of Medicine, Spilanthes acmella (L.) Murr. (Family - Asteraceae), is considered effective in the treatment of sexual deficiencies especially due to ageing. In the present study, characterization of ethanolic extracts of the Spilanthes acmella flower and its effect on general mating pattern, penile erection and serum hormone levels of normal male Wistar albino rats were investigated and compared with sildenafil citrate. In vitro nitric oxide release was also investigated in human corpus cavernosum cell line. As N-alkylamides are a promising group, their profiling was performed using a gradient reversed phase high performance liquid chromatography/electrospray ionization ion trap mass spectrometry (HPLC/ESI-MS) method on an embedded polar column. MS¹ and MS² fragmentation data were used for identification purposes. For assessment of sexual behavior, animals were divided into five groups of eight male rats. The extracts (50, 100 and 150 mg/kg body weight/day) and sildenafil citrate (5 mg/kg body weight/day) (positive control) were administered orally for 28 days. The behavioral and sexual parameters were observed at days 0, 15, 28 and after a lapse of 7 and 14 days of discontinuance of drug treatment. Five N-isobutylamides, one 2-methylbutylamide and one 2-phenylethylamide were identified. The orally administered extract had a dose dependent positive effect on mounting frequency, intromission frequency and ejaculation frequency and the most significant effects (p < 0.05) were observed at 150 mg/kg treatment, even after a lapse of 7 and 14 days of discontinuance of drug treatment. A dose dependent effect was also observed on the FSH, LH and testosterone serum levels. With 150 mg/kg of ethanolic extract the values for FSH, LH and testosterone were 3.10 ± 0.25 mlU/ml, 6.87 ± 0.18 mlU/ml and 3.72 ± 0.12 ng/ml, respectively. In vitro nitric oxide release was 21.7 ± 2.9 μM, which was significantly higher compared to the control group (p < 0.01). Sildenafil citrate exhibited also a significant effect on NO release, but no effect on hormone levels of rats was observed. The aphrodisiac potential of an ethanolic Spilanthes acmella extract was demonstrated in vitro and in vivo. N-Alkylamides might attribute to the improved sexual potential. Study lends support to the traditional utilization of S. acmella as a sexual stimulating agent.     

Is there an opiate receptor in the snail Megalobulimus sanctipauli? Action of morphine and naloxone

The effects of morphine sulfate (10, 15 and 20 mg/kg) or saline control (5 mg/kg) on the latency of the anterior body-lifting response to heat (avoidance response) were determined in four groups of snails Megalobulimus sanctipauli (n = 6) individually placed on a metal plate mounted on the surface of a water bath at 52 ± 1°C. The effects of pre-treatment with naloxone hydrochloride (5 mg/kg) or saline (2.5 ml/kg) control on the responses to morphine (15 mg/kg) were determined in two different groups of animals (n = 6). Administration of morphine resulted in an increase in the avoidance behavior latency with maximum effects occuring at 15 mg/kg, 10–15 min after injection. The effects of morphine disappeared within 90–120 min. Saline treatment had no detectable effects on the latency of the response to an aversive stimulus. Naloxone significantly blocked (P < 0.05, Student paired t-test) the increase in avoidance behavior latency. The present results indicate that: 1. morphine has an antinociceptive effect on the response of Megalobulimus sanctipauli to an aversive thermal stimulus; and 2. the morphine-induced “analgesia” may be caused by the stimulation of μ opiate receptors.     

Effect of oral imperatorin on memory in mice

The aim of this study was to explore the effect of the acetylcholinesterase inhibiting mixture of extracts of Angelica archangelica fruit and Geranium sylvaticum on memory. Furthermore the effect of the main compound, the furanocoumarin imperatorin, which has been shown to affect several neurotransmitters, was studied. Passive avoidance was measured by step-down latency and step-through latency of 10 months old mice receiving 0.79 mg/kg of imperatorin daily, pure or as part of the extracts, for 14 days or longer. Step-down latency was significantly higher in both groups receiving imperatorin than in the control group. In contrast, no difference was found between treatment groups regarding step-through latency. The results indicate that the imperatorin is the main active component of the extract mixture.