Involvement of monoaminergic systems in the antidepressant-like effect of Eugenia brasiliensis Lam. (Myrtaceae) in the tail suspension test in mice

Pharmacological Evidence of Eugenia Brasiliensis Leaves in a Reserpine-Induced Fibromyalgia Model: Antinociceptive, Emotional, Anti-Inflammatory, and Neurotrophic Effects

Fibromyalgia (FM) is a painful chronic condition that significantly impacts the quality of life, posing challenges for clinical management. Given the difficulty of understanding the pathophysiology and finding new therapeutics, this study explored the effects of a medicinal plant, E. brasiliensis, in an FM model induced by reserpine in Swiss mice. Animals were treated with saline 0.9% (vehicle), duloxetine 10 mg/kg (positive control), or hydroalcoholic extract of E. brasiliensis leaves 300 mg/kg (HEEb). Nociceptive parameters, as well as locomotion, motor coordination, strength, anxiety, and depressive-like behaviors, were evaluated for 10 days. After that, the brain and blood were collected for further analysis of cytokines (interleukin 1? and interleukin 6), brain-derived neurotrophic factor (BDNF), and the immunocontents of total and phosphorylated Tropomyosin receptor kinase B (TrkB). The results demonstrated that the acute and prolonged treatment with HEEb was able to reduce both mechanical and thermal nociception. It was also possible to observe an increase in the strength, without changing locomotion and motor coordination parameters. Interestingly, treatment with HEEb reduces anxious and depressive-like behaviors. Finally, we observed a reduction in inflammatory cytokines in the hippocampus of animals treated with HEEb, while an increase in BDNF was observed in the prefrontal cortex (PFC). However, no alterations related to total and phosphorylated TrkB receptor expression were found. Our study demonstrated the antinociceptive and emotional effects of HEEb in mice, possibly acting on neuroinflammatory and neurotrophic mechanisms. These data provide initial evidence about the E. brasiliensis potential for treating chronic pain.

Toxicological and pharmacological effects of Eugenia brasiliensis Lam. (Myrtaceae) leaves in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Eugenia brasiliensis Lam., popularly known as "grumixama" or "Brazilian cherry", is widely used in folk medicine with astringent, diuretic, energizing, anti-rheumatic, and anti-inflammatory properties.

AIM OF THE STUDY

Despite its traditional use, detailed toxicological studies of Eugenia brasiliensis are few. Thus, in the current study, we evaluate the toxicological effects of hydroalcoholic extract of Eugenia brasiliensis (HEEb) and its antinociceptive and anti-inflammatory activity.

MATERIALS AND METHODS

We used male, and female Swiss mice. Acute toxicity study was performed following the Organization for Economic Cooperation and Development (OECD) guideline 425, and subacute toxicity was assessed following OECD guideline 407. We observed behavioral responses, in addition to hematological, biochemical, and histological evaluations. The antinociceptive and anti-inflammatory activity of HEEb were assessed using the Carrageenan-induced mechanical allodynia and paw edema model. Mechanical allodynia, levels of inflammatory cytokines, and oxidative damage were evaluated.

RESULTS

The treatment with HEEb was not able to generate important toxicological alterations. Moreover, doses of 100 and 300 mg/kg of HEEb were able to reduce mechanical allodynia, paw edema, and inflammatory cytokines (TNF-α, IL-1β, and IL-6), decrease malondialdehyde and increase superoxide dismutase enzyme activity in the paw.

CONCLUSIONS

This study demonstrated that HEEb does not present important toxic effects. Additionally, an important antinociceptive, anti-inflammatory, and antioxidant potential were observed.

Involvement of monoaminergic system in the antidepressant effect of 3-substituted thietane-1,1-dioxide derivative

Introduction: The aim of the study was to assess the involvement of the monoaminergic system in the antidepressant effect of a new 3-substituted thietane-1,1-dioxide derivative (N-199/1) using tests with several pharmacological antagonists and agonists.

Materials and methods: We conducted 3 sets of experiments in white outbred male mice. In Experiment 1, we assessed the antidepressant effect of N-199/1 in the forced swimming test (FST) and tail suspension test (TST) when administered repeatedly for 2 weeks intraperitoneally (i.p.). In Experiment 2, we evaluated the antidepressant effect of N-199/1 in FST and TST when co-administered with 5HT1A- (WAY100635, 0.1 mg/kg), 5HT2A/2C- (ketanserin, 5 mg/kg), 5HT3- (ondansetron, 1 mg/kg) serotonergic and α2-adrenergic (yohimbine, 1 mg/kg) receptors antagonists. In Experiment 3, we assessed the effect of N-199/1 on the hypothermia induced by i.p. injection of α2-adrenergic receptors agonist clonidine (0.3 mg/kg).

Results and discussion: N-199/1 reduced immobility time (IT) and index of depression (ID) in FST, and did not affect IT in TST, either when administered repeatedly in Experiment 1, or acutely in Experiment 2. In Experiment 2, ketanserin enhanced the effect of N-199/1, decreasing ID by 36%, while WAY100635 and yohimbine antagonized it, increasing ID by 27% and IT by 115%, respectively, in comparison with N-199/1. N-199/1 attenuated the effect of ondansetron, increasing IT by 36%. In Experiment, 3 N-199/1 reduced clonidine-induced hypothermia 1 h after the injection of clonidine. N-199/1 exhibited pronounced antidepressant properties in FST, an agonism to 5HT1A-receptors and an antagonism to 5HT2A/2C- and α2-receptors in tests of neuropharmacological interaction, which indicates an atypical mechanism of its antidepressant action.

Conclusion: The antidepressant effect of N-199/1 is due to the stimulation of 5HT1A-receptors and blockade of 5HT2A/2C- and α2-receptors.

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Medicinal Plants in the Treatment of Depression: Evidence from Preclinical Studies

Medicinal plants and their extracts are natural remedies with enormous potential for treating various diseases, including depression and anxiety. In the case of depression, hundreds of plants have traditionally been used in folk medicine for generations. Different plant extracts and natural products have been analyzed as potential antidepressant agents with validated models to test for antidepressant-like effects in animals, although other complementary studies have also been employed. Most of these studies focus on the possible mediators implicated in these potential effects, with dopamine, serotonin, and noradrenaline being the principal neurotransmitters implicated, both through interference with receptors and with their metabolism by monoamino oxidases, as well as through neuro-endocrine and neuroprotective effects. There are approximately 650 reports of antidepressant-like medicinal plants in PubMed; 155 of them have been compiled in this review, with a relevant group yielding positive results. Saffron and turmeric are the most relevant species studied in both preclinical and clinical studies; St. John's wort or kava have also been tested extensively. To the best of our knowledge, no review to date has provided a comprehensive understanding of the biomolecular mechanisms of action of these herbs or of whether their potential effects could have real benefits. The purpose of this narrative review is to provide an update regarding medicinal plants from the year 2000 to the present to examine the therapeutic potential of these antidepressant-like plants in order to contribute to the development of new therapeutic methods to alleviate the tremendous burden that depression causes worldwide.

Salvia officinalis and Lippia triphylla: Chemical characterization and evaluation of antidepressant-like activity

Salvia officinalis (Lamiaceae) and Lippia triphylla (Verbenaceae) are two plants known for their therapeutic effects in conventional medicine for the treatment of a wide extent of diseases, including the ones on the central nervous system. In the present study, the impact of aqueous extract from the leaves of these two herbs for the treatment of depression was examined. The phytochemical profile highlighted the presence of eighteen and ten polyphenolic compounds in Salvia officinalis and Lippia triphylla, respectively. The antidepressant effects of such extracts were assessed using two tests: the forced swimming test (FST) and tail suspension test (TST) in swiss albino mice. Five mice were partitioned into each group: control (distilled water), standard (Imipramine hydrochloride, 25 mg/kg) and three test ones treated with increased doses of aqueous extracts (250-500-1000 mg/kg), orally administered for two weeks. The acute treatment of the mice with aqueous extracts of Salvia officinalis and Lippia triphylla reduced significantly the time of immobility in the forced swimming test (p < 0.001) as compared to control group, and also decreased significantly the time of immobility of mice in the tail suspension test (p < 0.001). The findings attained in this work show how both plants possess potential anti-depressant-like effects; however, the translation from the results presented in this work to a potential use as therapeutic agents would require the acquisition of a stronger scientific evidence.

Multiple cellular targets involved in the antidepressant-like effect of glutathione

A previous study demonstrated that glutathione (GSH) produces specific antidepressant-like effect in the forced swimming test (FST), a predictive test of antidepressant activity. The present study investigated the involvement of multiple cellular targets implicated in the antidepressant-like effect of GSH in the FST. The antidepressant-like effect of GSH (300 nmol/site, icv) lasted up to 3 h when mice were submitted to FST. The central administration of oxidized GSH (GSSG, 3-300 nmol/site) did not alter the behavior of mice submitted to the FST. Furthermore, the combined treatment of sub-effective doses of GSH (100 nmol/site, icv) with a sub-effective dose of classical antidepressants (fluoxetine 10 mg/kg, and imipramine 5 mg/kg, ip) presented synergistic effect by decreasing the immobility time in the FST. The antidepressant-like effect of GSH was abolished by prazosin (1 mg/kg, ip, α₁-adrenoceptor antagonist), baclofen (1 mg/kg, ip, GABAB receptor agonist), bicuculline (1 mg/kg, ip, GABAA receptor antagonist), l-arginine (750 mg/kg, ip, NO precursor), SNAP (25 μg/site, icv, NO donor), but not by yohimbine (1 mg/kg, ip, α₂-adrenoceptor antagonist). The NMDA receptor antagonists, MK-801(0.001 mg/kg, ip) or GMP (0.5 mg/kg, ip), potentiated the effect of a sub-effective dose of GSH in the FST. These results suggest that the antidepressant-like effect induced by GSH is connected to the activation of α1 adrenergic and GABAA receptors, as well as the inhibition of GABAB and NMDA receptors and NO biosyntesis. We speculate that redox-mediated signaling on the extracelular portion of cell membrane receptors would be a common mechanism of action of GSH.

Wild Brazilian species of Eugenia genera (Myrtaceae) as an innovation hotspot for food and pharmacological purposes

The Myrtaceae is one of the most common plant families in Brazil, including >1000 species of native fruit spread from North to South, where around 50% of all species are endemic to the Atlantic Rain Forest Biome. Most Brazilian species belong to Eugenia, Campomanesia, Psidium and Myrciaria genera. In general, they are characterized by the presence of leaves opposite, simple, entire, with pellucid glands containing ethereal oils and produces berry-like, fleshy fruits with a wide diversity of beneficial characteristics. Several parts of these plants are widely used in regional folk medicine as an astringent, anti-inflammatory, antihypertensive, to treat gastrointestinal disorders, and so on. Some species have already been studied and most of their metabolic effects are attributed to the presence of polyphenols, carotenoids as well as sesquiterpenes and monoterpenes. In addition, the Myrtaceae family has great economic potential, because of the sensory characteristics which encourages their commercial exploitation plus the presence of phytochemicals which play an important role in managing several degenerative chronic diseases besides representing a hotspot of technological innovation for food, cosmetic and pharmaceutical purposes. In this context, this review discusses about the importance of some Eugenia genera representatives such as Eugenia uniflora, Eugenia stipitata, Eugenia brasiliensis, Eugenia pyriformis and Eugenia dysenterica, emphasizing its profile of bioactive compounds as well as the knowledge of the nutritional and functional fruit potential, providing information for further studies aiming to stimulate the cultivation of Brazilian wild berries, for consumption and new food ingredients.

Antioxidant and antidepressant-like effects of Eugenia catharinensis D. Legrand in an animal model of depression induced by corticosterone

This work investigated the antioxidant and antidepressant-like effects of ethyl acetate extract from Eugenia catharinensis in mice treated with corticosterone (20 mg/Kg). The animals received saline or corticosterone (21 days) and, in the last 7 days, they were treated with the extract (50, 125, 200 or 250 mg/Kg) or vehicle. After 24 h, the mice were submitted to the open field and forced swimming tests, after which the hippocampus and cerebral cortex were removed. Our results showed that the extract decreased the immobility time of mice in the forced swimming test and that the extract was able to reverse the effect caused by corticosterone. Corticosterone pre-treatment generated oxidative stress, altering antioxidant enzymes in the nervous tissue. The extract increased the catalase and superoxide dismutase activities and reversed the effects of corticosterone. In the hippocampus, the extract increased superoxide dismutase activity and reversed the increase in catalase activity elicited by corticosterone. We propose that the effects elicited by the Eugenia catharinensis are dependent on the presence of phenolic compounds (gallic acid, protocatechuic acid, syringic acid, 4-hydroxy methylbenzoic acid, chlorogenic acid, salicylic acid, caffeic acid, vanillic acid, p-coumaric acid, isoquercetin, rutin, ferulic acid, aromadendrin, galangin and apigenin) in this extract, as demonstrated by HPLC-ESI-MS/MS.

Eugenia brasiliensis leaves extract attenuates visceral and somatic inflammatory pain in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Eugenia brasiliensis Lam. (Myrtaceae) is a Brazilian tree distributed throughout Atlantic rain forest, since Bahia until Santa Catarina state, and is popularly known as "grumixaba, grumixameira, cumbixaba, ibaporoiti, and cereja-brasileira". The bark and leaves of Eugenia brasiliensis are used in folk medicine as adstringent, diuretic, energizing, anti-rheumatic and anti-inflammatory. This study aimed at investigating the chemical composition, antinociceptive and anti-inflammatory effect of the hydroalcoholic extract of Eugenia brasiliensis (HEEb).

MATERIAL AND METHODS

Chemical composition of the HEEb was determined by High Performance Liquid Chromatography/ESI-Mass Spectrometry (HPLC-ESI-MS/MS). The antinociceptive and anti-inflammatory effects of HEEb (30-300 mg/kg) was verified in mice after oral administration by intra-gastric gavage (i.g.) 60 min prior to experimentation. It was investigated whether HEEb decreases visceral pain and leukocyte migration induced by an intraperitoneal (i.p.) injection of acetic acid (0.6%). We also evaluated whether HEEb decreases nociceptive behavior induced by formalin (including paw edema and temperature), prostaglandin E₂ (PGE₂), histamine, and compound 48/80. Finally, we evaluated the effect of HEEb in the chronic inflammatory (mechanical and thermal hypersensitivity) pain induced by complete Freund's adjuvant (CFA), as well as quantifying the concentration of the pro-inflammatory cytokines TNF-α and IL-6 in the paw by ELISA method.

RESULTS

Seven polyphenols were identified in HEEb by HPLC-ESI-MS/MS analysis. HEEb treatment alleviated nocifensive behavior and leukocyte migration caused by acetic acid. Moreover, HEEb also reduced the inflammatory pain and paw temperature induced by formalin, as well as it decreased nociceptive behavior induced by histamine and compound 48/80. Finally, acute and repeated treatment of animals with HEEb (100 mg/kg, i.g.) markedly reduced the mechanical and thermal (heat) hypersensitivity, besides decrease paw edema and temperature induced by CFA, and this effect was evident until the day 7. Moreover, repeated treatment with HEEb (100 mg/kg, i.g.) significantly reduced the levels of IL-6 and TNF-α in the paw when compared to the CFA group.

CONCLUSIONS

This is the first report showing that HEEb presents antinociceptive and anti-inflammatory effects in the visceral and somatic inflammatory pain in mice, possibly involving the inhibition of histamine receptors and pro-inflammatory cytokines activated pathways. Our results are of interest because they support the use of Eugenia brasiliensis as a potential source of phytomedicine for inflammatory diseases and pain.

Biphasic Effects of α-Asarone on Immobility in the Tail Suspension Test: Evidence for the Involvement of the Noradrenergic and Serotonergic Systems in Its Antidepressant-Like Activity

Alpha (α)-asarone is one of the main psychoactive compounds, present in Acorus species. Evidence suggests that the α-asarone possess an antidepressant-like activity in mice. However, the exact dose-dependent effect of α-asarone and mechanism(s) involved in the antidepressant-like activity are not clear. The present study aimed to investigate the dose-dependent effect of α-asarone and the underlining mechanism(s) involved in the antidepressant-like activity of α-asarone in the mouse model of tail suspension test (TST). In this study, the acute effect of α-asarone per se at different doses (10–100 mg/kg, i.p.) on immobility in the TST was studied. Additionally, the possible mechanism(s) involved in the antidepressant-like effect of α-asarone was studied using its interaction with noradrenergic and serotonergic neuromodulators in the TST. The present results reveal that the acute treatment of α-asarone elicited biphasic responses on immobility such that the duration of the immobility time is significantly reduced at lower doses (15 and 20 mg/kg, i.p.) but increased at higher doses (50 and 100 mg/kg, i.p.) in the TST. Besides, α-asarone at higher doses (50 and 100 mg/kg, i.p.) significantly decreased the spontaneous locomotor activity. Moreover, pretreatment of mice with noradrenergic neuromodulators such as AMPT (100 mg/kg, i.p., a catecholamine synthesis inhibitor), prazosin (1 mg/kg, i.p., an α₁-adrenoceptor antagonist), yohimbine (1 mg/kg, i.p., an α₂-adrenoceptor antagonist) and with serotonergic neuromodulators such as PCPA (100 mg/kg, i.p., once daily for four consecutive days, a serotonin synthesis inhibitor,) and WAY100635 (0.1 mg/kg, s.c., a selective 5-HT_1A receptor antagonist) significantly reversed the anti-immobility effect of α-asarone (20 mg/kg, i.p.). Taken together, our results suggest that the acute treatment with α-asarone elicited biphasic actions in the TST in which antidepressant-like effect was seen at relatively lower doses (15 and 20 mg/kg, i.p.) and depressive-like activity at relatively higher doses (50 and 100 mg/kg, i.p.). Furthermore, it has been revealed that the antidepressant-like effect of α-asarone could be mediated through both noradrenergic (α₁ and α₂ adrenoceptors) and serotonergic (particularly, 5-HT_1A receptors) systems.

Identification of Ellagitannins and Flavonoids from Eugenia brasilienses Lam. (Grumixama) by HPLC-ESI-MS/MS

The grumixama (Eugenia brasiliensis Lam.), also known as Brazilian cherry, is a fruit native to Brazil. This study identified the flavonoids in the flesh and seeds and ellagitannin in the flesh of purple and yellow varieties. The physicochemical characteristics and antioxidant capacity of these fruits were also evaluated. Anthocyanins and flavonols were found in high levels in the flesh of purple (32-180 mg 100 g(-1) FW) and yellow grumixama (13-41 mg 100 g(-1) FW), respectively. The major flavonoids identified were cyanidin 3-glucoside and quercetin aglycone. Furthermore, ellagitannins were found in high levels in the flesh of purple (82-243 mg ellagic acid equiv 100 g(-1) FW) and yellow grumixama (92 mg ellagic acid equiv 100 g(-1) FW) and seeds (2220-2905 mg ellagic acid equiv 100 g(-1) FW). The ellagitannin profiles of both varieties were first characterized in which pedunculagin isomers, strictinin isomers, and ellagic acid galloyl hexoside were the major ellagitannins identified. In summary, both varieties of the grumixama fruit as well as the seeds could be good sources of bioactive compounds, mainly ellagitannins.

Involvement of the catecholaminergic system on the antidepressant-like effects of Alpinia zerumbet in mice

CONTEXT

The traditional uses of Alpinia zerumbet (Pers.) B.L.Burtt & R.m.SM (Zingiberaceae), popularly known as colonia or pacová, suggest that the species has antihypertensive, diuretic, and sedative properties. We previously reported that an ethanol extract of Alpinia zerumbet (HEA) significantly reduced the immobility time in the tail suspension test (TST), similar to the tricyclic antidepressant imipramine. Moreover, HEA presented antioxidant and anxiolytic-like effects in mice.

OBJECTIVE

The objective of this study is to investigate the involvement of monoaminergic and glutamatergic systems in the antidepressant-like effects of this species.

MATERIALS AND METHODS

A hydroethanolic extract prepared with the leaves of A. zerumbet was assayed in the TST in male Swiss mice (800 mg/kg, p.o.). Synthesis inhibitors (AMPT, inhibitor of tyrosine hydroxylase, 100 mg/kg, i.p.; and PCPA, irreversible tryptophan hydroxylase inhibitor, 100 mg/kg, i.p.) and a specific glutamate antagonist (AMPA receptor antagonist NBQX, 10 mg/kg, i.p.) were used prior testing.

RESULTS

Pre-treatment with the noradrenergic/dopaminergic inhibitor AMPT fully abolished the anti-immobility effects of HEA, with the two-way ANOVA yielding a significant interaction between pre-treatment and treatment (F1,32 = 10.0, p < 0.01); no interaction was observed with the serotonergic inhibitor PCPA (F1,32 = 0.33, p > 0.05) or NBQX (F1,32 = 0.21, p > 0.05).

CONCLUSION

These results indicated that HEA most likely acts through the dopaminergic and/or noradrenergic system but not through the serotoninergic or glutamatergic systems. This study reinforces the idea that the available biodiversity in Brazil can serve as a basis for innovation in the development of new drugs.

Eugenia uniflora leaves essential oil induces toxicity in Drosophila melanogaster: involvement of oxidative stress mechanisms

Eugenia unifloraL. (Myrtaceae family), also known as “pitanga”, is a tree species widely used in popular medicine.

Serotonergic and noradrenergic systems are implicated in the antidepressant-like effect of ursolic acid in mice

Ursolic acid (UA) is a natural pentacyclic triterpenoid carboxylic acid that exerts antidepressant-like effects in the tail suspension test (TST) and in the forced swimming test, and this effect was reported to be mediated by the dopaminergic system. Many studies show that currently available antidepressant agents have effects on multiple neurotransmitter systems which account for their efficacy. Therefore, this study was aimed at investigating the possible involvement of the serotonergic, noradrenergic, glutamatergic and opioid systems in the antidepressant-like effect of UA. To this end, several pharmacological agents were administered to verify their ability to influence the antidepressant-like responses elicited by UA in the TST in mice. The open-field test was used to assess the locomotor activity. The results show that the pre-treatment of mice with ρ-chlorophenylalanine (100mg/kg, i.p., 4 days) or α-methyl-ρ-tyrosine (100mg/kg, i.p.) but not with N-methyl-d-aspartate (0.1 pmol/mouse, i.c.v.) or naloxone (1mg/kg, i.p.), was able to prevent the antidepressant-like effect of UA (0.1mg/kg, p.o.). Sub-effective doses of fluoxetine (5mg/kg, p.o.) or reboxetine (2mg/kg, p.o.), but not ketamine (0.1mg/kg, i.p.) or MK-801 (0.001 mg/kg, p.o.), was capable of potentiating the effect of a sub-effective dose of UA (0.001 mg/kg, p.o.) in the TST. None of the treatments affected locomotor activity. Altogether, the results show an involvement of the serotonergic and noradrenergic systems, but not the glutamatergic or opioid systems, in the antidepressant-like effect of UA.

Antidepressant-like effects of the hydroalcoholic extracts of Hemerocallis citrina and its potential active components

Background

Herbal therapies are potential alternatives and adjuncts for depression treatment. The present study aims to investigate the antidepressant-like effects of hydroalcoholic Hemerocallis citrina extracts and its potential neuropharmacological components.

Methods

Hydroalcoholic H. citrina extracts were phytochemically analyzed. Behavioral models, including tail suspension tests and open field tests, were performed to evaluate the antidepressant-like effects of the extracts. A possible mechanism was explored by analyzing brain monoamine neurotransmitters. Toxicity and histopathological analyses were performed to determine whether or not the extracts are safe for oral administration.

Results

The antidepressant-like effects of hydroalcoholic H. citrina extracts were mainly related to flavonoids, especially rutin and hesperidin. The extract prepared using 75% ethanol (i.e., HCE75) exhibited the highest active flavonoid content and activity. Orally administered 400 mg/kg of HCE75 significantly induced an antidepressant-like effect, whereas the combination of equivalent rutin and hesperidin dosages exhibited the same profiles. Isobologram analysis showed sub-additive antidepressant interactions between rutin and hesperidin. HCE75 (400 mg/kg, p.o.) increased the serotonin and dopamine levels in the central nervous system. Mortality and lesions were not observed upon oral administration of up to 5000 mg/kg HCE75.

Conclusions

The antidepressant-like effects of hydroalcoholic H. citrina extracts are mainly related to flavonoids, especially rutin and hesperidin. The serotonergic and dopaminergic systems may have major roles. The active extract is toxicologically safe for oral administration.

Antidepressant effects of insulin in streptozotocin induced diabetic mice: Modulation of brain serotonin system

Diabetes is a persistent metabolic disorder, which often leads to depression as a result of the impaired neurotransmitter function. Insulin is believed to have antidepressant effects in depression associated with diabetes; however, the mechanism underlying the postulated effect is poorly understood. In the present study, it is hypothesized that insulin mediates an antidepressant effect in streptozotocin (STZ) induced diabetes in mice through modulation of the serotonin system in the brain. Therefore, the current study investigated the antidepressant effect of insulin in STZ induced diabetes in mice and insulin mediated modulation in the brain serotonin system. In addition, the possible pathways that lead to altered serotonin levels as a result of insulin administration were examined. Experimentally, Swiss albino mice of either sex were rendered diabetic by a single intraperitoneal (i.p.) injection of STZ. After one week, diabetic mice received a single dose of either insulin or saline or escitalopram for 14days. Thereafter, behavioral studies were conducted to test the behavioral despair effects using forced swim test (FST) and tail suspension test (TST), followed by biochemical estimations of serotonin concentrations and monoamine oxidase (MAO) activity in the whole brain content. The results demonstrated that, STZ treated diabetic mice exhibited an increased duration of immobility in FST and TST as compared to non-diabetic mice, while insulin treatment significantly reversed the effect. Biochemical assays revealed that administration of insulin attenuated STZ treated diabetes induced neurochemical alterations as indicated by elevated serotonin levels and decreased MAO-A and MAO-B activities in the brain. Collectively, the data indicate that insulin exhibits antidepressant effects in depression associated with STZ induced diabetes in mice through the elevation of the brain serotonin levels.

Involvement of serotoninergic and adrenergic systems on the antidepressant-like effect of E. uniflora L. leaves essential oil and further analysis of its antioxidant activity

In this work we evaluated antidepressant-like effect of E. uniflora leaves EO employing the tail suspension test. The involvement of serotonergic and adrenergic systems was appraised. EO was administered by oral route (p.o.) in mice and the doses of 10 and 50mg/kg exhibited antidepressant-like action in the TST. The effect of EO (10mg/kg) was prevented by the pretreatment of mice with ketanserin (5mg/kg, intraperitoneal), prazosin (0.1mg/kg, i.p.) and yohimbine (0.1mg/kg, i.p.). In addition, further analysis of the in vitro antioxidant effect of the EO was made against lipid oxidation. The results revealed that EO has a potent antioxidant activity and therapeutic potential for the development of phytomedicines with antidepressant and antioxidant properties.