Involvement of the GABAA Receptor in the Antidepressant-Like Effects Produced by Low and High Doses of the Flavonoid Chrysin in the Rat: A Longitudinal Study.

BACKGROUND: The flavonoid chrysin produces rapid and long-lasting anxiolytic- and antidepressant-like effects in rats. However, it is not known whether low and high doses of chrysin produce differential anti-immobility effects through the Gamma-Aminobutyric Acid sub-type A (GABAA) receptor. The goal of this work was therefore to compare low and high doses of chrysin for their effects on depression-like behavior in a longitudinal study. Moreover, chrysin was compared with the serotonergic fluoxetine and Gamma-Aminobutyric Acid (GABA)ergic allopregnanolone, and its involvement with the GABAA receptor after chronic treatment was also investigated. METHODS: Male Wistar rats were assigned to five groups (n = 8 each): vehicle, 1 mg/kg chrysin, 5 mg/kg chrysin, 1 mg/kg fluoxetine, and 1 mg/kg allopregnanolone. In the first experiment, treatments were injected daily and the effects on locomotor activity and the forced swim test were evaluated at 0, 1, 14, and 28 days of treatment, and 48 h after the final treatment. In the second experiment, similar groups were treated for 28 days with injection of 1 mg/kg picrotoxin to investigate the role of the GABAA receptor. Depending on the experimental design, one- and two-way analysis of variance (ANOVA) tests were used for statistical analysis, with p < 0.05 set as the criteria for significance. RESULTS: In both experiments, the treatments did not alter locomotor activity. However, low and high doses of chrysin, allopregnanolone, and fluoxetine gradually produced antidepressant-like effects in the forced swim test, and maintained this effect for 48 h post-treatment, except with low dose chrysin. Picrotoxin blocked the antidepressant-like effects produced by low dose chrysin, but did not affect those produced by high dose chrysin, allopregnanolone, or fluoxetine. CONCLUSIONS: The differential antidepressant-like effects caused by low and high doses of chrysin are time-dependent. Low dose chrysin produces a rapid antidepressant-like effect, whereas high dose chrysin produces a delayed but sustained the effect, even 48 h after withdrawal. The effect with high dose chrysin was similar to that observed with allopregnanolone and fluoxetine. The mechanism for the antidepressant-like effect of low chrysin appears to be GABAergic, whereas the effect of high dose chrysin may involve other neurotransmission and neuromodulation systems related to the serotonergic system.

Effect of Cucurbita ficifolia Bouché on glutathione level and glycosylated hemoglobin percentage in a Mexican rural population with type 2 diabetes.

ETHNOPHARMACOLOGICAL IMPORTANCE: Cucurbita ficifolia Bouché fruit is widely used in Mexican traditional medicine to treat type 2 diabetes (T2D) because it has been attributed with antioxidant and hypoglycemic properties in different experimental models and T2D patients. An imbalance in physiological glutathione (GSH) concentrations increases the susceptibility to developing complications associated with oxidative stress in T2D patients. AIM OF THE STUDY: To investigate the effect of C. ficifolia on the antioxidant properties of GSH, general health measurements, and biochemical parameters in a Mexican rural population, and to evaluate the changes in socio-affective scores of patients due to improvement in T2D. MATERIALS AND METHODS: Twenty-seven women diagnosed with T2D with poor glycemic control volunteered and were divided into two groups: C. ficifolia (0.5 g/kg of fresh pulp weight) with hypoglycemic pharmacotherapy, and another group with only hypoglycemic pharmacotherapy, for 12 weeks. We evaluated the effect of the fresh pulp of C. ficifolia on body mass index, blood pressure, glucose, glycosylated hemoglobin, cholesterol, triglycerides, and GSH. Expanding the study, we evaluated the quality of life, anxiety, and depression scores before and after the intervention. RESULTS: Treatment with the fresh pulp of C. ficifolia for 12 weeks reduced glycosylated hemoglobin, similar to the hypoglycemic pharmacotherapy group, and significantly increased GSH concentrations. The patients' moods did not change despite increased GSH concentrations and improved T2D control. CONCLUSIONS: The increased GSH concentrations due to the consumption of fresh pulp of C. ficifolia could help to protect against oxidative stress and extend therapeutic benefits in addition to the usual hypoglycemic drugs in patients with T2D.

The standardized extract of Centella asiatica L. Urb attenuates the convulsant effect induced by lithium/pilocarpine without affecting biochemical and haematological parameters in rats.

BACKGROUND: Status epilepticus (SE) is a type of epileptic activity characterized by a failure of the inhibitory mechanisms that limit seizures, which are mainly regulated by the GABAergic system. This imbalance increases glutamatergic neurotransmission and consequently produces epileptic activity. It is also associated with oxidative stress due to an imbalance between reactive oxygen species (ROS) and antioxidant defences. Unfortunately, long-term treatment with anti-epileptic drugs (AEDs) may produce hepatotoxicity, nephrotoxicity, and haematological alterations. In this way, some secondary metabolites of plants have been used to ameliorate the deterioration of nervous system disorders through their antioxidant properties, in addition to their anticonvulsant effects. An example is Centella asiatica, a plant noted to have a reputed neuroprotective effect related to its antioxidant activity. However, similar to conventional drugs, natural molecules may produce side effects when consumed in high doses, which could occur with Centella asiatica. Therefore, we aimed to evaluate the effect of a standardized extract of Centella asiatica L. Urb with tested anticonvulsant activity on biochemical and haematological parameters in rats subjected to lithium/pilocarpine-induced seizures. METHODS: Twenty-eight adult male Wistar rats were randomly divided into four groups (n = 7 each): vehicle (purified water), Centella asiatica (200 and 400 mg/kg), and carbamazepine (CBZ) (300 mg/kg) as a pharmacological control of anticonvulsant activity. Treatments were administered orally every 24 h for 35 consecutive days. On Day 36, SE was induced using the lithium/pilocarpine model (3 mEq/kg, i.p. and 30 mg/kg s.c., respectively), and the behavioural and biochemical effects were evaluated. RESULTS: Centella asiatica 400 mg/kg increased the latency to the first generalized seizure and SE onset and significantly reduced the time to the first generalized seizure compared to values in the vehicle group. Biochemical parameters, i.e., haematic cytometry, blood chemistry, and liver function tests, showed no significant differences among the different treatments. CONCLUSION: The dose of Centella asiatica that produces anticonvulsant activity in the lithium/pilocarpine model devoid of hepatotoxicity, nephrotoxicity, and alterations in haematological parameters suggests that the standardized extract of this plant could be of utility in the development of new safe therapies for the treatment of convulsions associated with epilepsy.

TPH2-703 G/T polymorphism is associated with stress, depression, and psychosocial symptoms in mentally healthy Mexicans.

Tryptophan hydroxylase (TPH) catalyzes the rate-limiting step of serotonin synthesis. TPH2 is the brain-specific isoform of this enzyme, and genetic variations in the TPH2 gene have been shown to impact its transcription and enzymatic activity and are associated with mood disorders. In this study we focused on the rs4570625 (-703G/T) single nucleotide polymorphism of TPH2 gene. By using conventional polymerase chain reaction (PCR), we examined the effect of this polymorphism on stress, anxiety, and depression symptoms as well as quality of life, evaluated based on the Holmes-Rahe Inventory, the Beck Anxiety Inventory, the Beck Depression Inventory, and the World Health Organization Quality of Life - Short Version, respectively. We found that individuals with the homozygous recessive T/T genotype had lower stress and depression scores. In addition, the quality of life in the psychological health domain was better in males with the T/T genotype. These results suggest that T/T genotype could decrease the susceptibility to developing stress and depression in the Mexican population without a diagnosis for an emotional disorder.

A Comparative Study of Metabolic Syndrome Using NCEP-ATP III and IDF Criteria in Children and Its Relationship with Biochemical Indicators in Huatusco, Veracruz, Mexico.

Metabolic syndrome includes a set of metabolic alterations associated with overweight and obesity. The criteria for its diagnosis are heterogeneous, and there have been few studies about prevalence in the pediatric population. The aim of this study was to describe how the estimated prevalence of metabolic syndrome varies by International Diabetes Federation (IDF) vs. National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATP) criteria. We conducted a cross-sectional study in which anthropometric information, triglyceride, cholesterol, glycemia, and insulin levels, among others, were collected. We compared the group potentially misclassified by IDF with the group classified without metabolic syndrome by NCEP-ATP with respect to weight status and biomarkers. Statistical analysis included linear regression, Mann-Whitney U test, Fisher´s exact test, and odds ratio calculation. The IDF criteria missed the association with obesity, although the undetected group differed significantly from the nonmetabolic syndrome group in terms of IBM and weight. The associated biomarkers were ultrasensitive C-reactive protein (Hs-CRP), alanine aminotransferase (ALT) enzyme, insulin, triglycerides, and high-density lipoprotein (HDL) cholesterol. Waist circumference was the parameter with the strongest association for presenting metabolic syndrome, with an odds ratio of 18.33. The results of this study showed the estimated prevalence of MS varies by criteria, due to cutoff points, and how the high prevalence of MS strongly associated with obesity.

Behavioral Despair Is Blocked by the Flavonoid Chrysin (5,7-Dihydroxyflavone) in a Rat Model of Surgical Menopause.

Women have a high susceptibility to the negative effects of stress. Hormonal changes experienced throughout their reproductive life partially contribute to a higher incidence of anxiety and depression symptoms, particularly, during natural or surgical menopause. In preclinical research, the flavonoid chrysin (5,7-dihydroxyflavone) exerts anxiolytic- and anti-despair-like effects; however, it is unknown whether chrysin exerts a protective effect against the behavioral changes produced by acute stress on locomotor activity and behavioral despair in rats at 12-weeks post-ovariectomy. Ovariectomized female Wistar rats were assigned to eight groups: vehicle group (10% DMSO), three groups with chrysin and three groups with the same dose of allopregnanolone (0.5, 1, and 2 mg/kg), and one group with diazepam (2 mg/kg). The treatments were administered for seven consecutive days and the effects were evaluated in the locomotor activity and swimming tests. Chrysin (2 mg/kg) increased the latency to first immobility and decreased the total immobility time in the swimming test as the reference drugs allopregnanolone and diazepam (2 mg/kg); while locomotor activity prevented the behavioral changes produced by swimming. In conclusion, chrysin exerts a protective effect against the behavioral changes induced by acute stress, similarly to the neurosteroid allopregnanolone and the benzodiazepine diazepam in rats subjected to a surgical menopause model.

Participation of the Serotonergic System and Brain-Derived Neurotrophic Factor in the Antidepressant-like Effect of Flavonoids.

Depressive disorders are among the most disabling diseases experienced around the world, and their incidence has significantly increased over the last few decades due to multiple environmental, social, and biological factors. The search for new pharmacological alternatives to treat depression is a global priority. In preclinical research, molecules obtained from plants, such as flavonoids, have shown promising antidepressant-like properties through several mechanisms of action that have not been fully elucidated, including crossing of the blood brain barrier (BBB). This review will focus on discussing the main findings related to the participation of the serotonergic system and brain-derived neurotrophic factor (BDNF) on the antidepressant-like effect of some flavonoids reported by behavioral, neurochemical, and molecular studies. In this sense, evidence shows that depressive individuals have low levels of serotonin and BDNF, while flavonoids can reverse it. Finally, the elucidation of the mechanism used by flavonoids to modulate serotonin and BDNF will contribute to our understanding of the neurobiological bases underlying the antidepressant-like effects produced by these natural compounds.

Effects of Palmitoylethanolamide (PEA) on Nociceptive, Musculoskeletal and Neuropathic Pain: Systematic Review and Meta-Analysis of Clinical Evidence.

Some 30−50% of the global population and almost 20% of the European population actually suffer from chronic pain, which presents a tremendous burden to society when this pain turns into a disability and hospitalization. Palmitoylethanolamide (PEA) has been demonstrated to improve pain in preclinical contexts, but an appraisal of clinical evidence is still lacking. The present study aimed at addressing the working hypothesis for the efficacy of PEA for nociceptive musculoskeletal and neuropathic pain in the clinical setting. The systematic search, selection and analysis were performed in agreement with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 recommendations. The primary outcome was pain reduction, as measured by a pain assessment scale. The secondary outcome was improvement in quality of life and/or of parameters of function. The results obtained for a total of 933 patients demonstrate the efficacy of PEA over the control (p < 0.00001), in particular in six studies apart from the two randomized, double-blind clinical trials included. However, the results are downgraded due to the high heterogeneity of the studies (I2 = 99%), and the funnel plot suggests publication bias. Efficacy in achieving a reduction in the need for rescue medications and improvement in functioning, neuropathic symptoms and quality of life are reported. Therefore, adequately powered randomized, double-blind clinical trials are needed to deepen the domains of efficacy of add-on therapy with PEA for chronic pain. PROSPERO registration: CRD42022314395.

Anticonvulsant Effect of Turmeric and Resveratrol in Lithium/Pilocarpine-Induced Status Epilepticus in Wistar Rats.

Epilepsy is a chronic neurological disorder that lacks a cure. The use of plant-derived antioxidant molecules such as those contained in turmeric powder and resveratrol may produce short-term anticonvulsant effects. A total of 42 three-month-old male Wistar rats were divided into six groups (n = 7 in each group): Vehicle (purified water), turmeric (150 and 300 mg/kg, respectively), and resveratrol (30 and 60 mg/kg, respectively), administered per os (p.o.) every 24 h for 35 days. Carbamazepine (300 mg/kg/5 days) was used as a pharmacological control for anticonvulsant activity. At the end of the treatment, status epilepticus was induced using the lithium-pilocarpine model [3 mEq/kg, intraperitoneally (i.p.) and 30 mg/kg subcutaneously (s.c.), respectively]. Seizures were evaluated using the Racine scale. The 300 mg/kg of turmeric and 60 mg/kg of resveratrol groups had an increased latency to the first generalized seizure. The groups treated with 150 and 300 mg/kg of turmeric and 60 mg/kg of resveratrol also had an increased latency to status epilepticus and a decreased number of generalized seizures compared to the vehicle group. The chronic administration of turmeric and resveratrol exerts anticonvulsant effects without producing kidney or liver damage. This suggests that both of these natural products of plant origin could work as adjuvants in the treatment of epilepsy.

Assessment of executive functions and physical activity in girls and boys with normal weight, overweight and obesity.

OBJECTIVE: To evaluate the association between body mass index (BMI) and performance of executive functions (EFs) in girls and boys with 9- and 10-year-old schoolchildren with moderate- to vigorous-intensity physical activity (MVPA) and sedentary behaviour. METHODS: A total of 120 schoolchildren (61 girls and 59 boys) were evaluated anthropometrically. The MVPA was evaluated with a self-report questionnaire. EFs were measured using a neuropsychological battery of Executive Functions and Frontal Lobes-2 (BANFE-2). RESULTS: A high BMI was associated with longer delay in completing inhibitory control tests (p = 0.00, rp  = 0.32) and working memory (p = 0.00, rp  = 0.26). We observed correlations in time (p = 0.00, rp  = -0.43) and hits (p = 0.04, rp  = -0.27) of self-directed signalling test in boys; and girls in alphabetical words order (p = 0.00, rp  = -0.39). Active normal weight schoolchildren (ANw) performed better by successfully completed the working memory tasks (H = 26.97, p = 0.00) than sedentary schoolchildren with overweight and obesity. In addition, overweight-active schoolchildren (AOw) showed better performance on working memory tests in time (p = 0.00) and hits (p = 0.01) than their sedentary peers. Multiple linear regression analysis revealed a significant association between BMI and EFs scores (F = 2.41, df = 98, p = 0.001). CONCLUSIONS: EFs are affected by a high BMI and sedentary behaviour in school children. Boys and girls reflected differences to solve the same challenges. The MVPA has a positive effect on executive control skills mainly in overweight children.

Optimizing rat and human blood cells sampling for in silico morphometric analysis.

Measurements of Morphometric Parameters of the Blood Cells (MPBC) are key for the diagnosis of both mental and metabolic diseases. Several manual approaches or computational methodologies are useful to provide reliable clinical diagnosis. The sample processing and data analysis is relevant, however the sample handling on the pre-analytical phase remains scarcely evaluated. The main goal of this study was to favor the preservation of blood smear using a histological resin. This strategy lead us two practical approaches, give a detailed morphometric description of white blood cells and establish reference intervals in male Wistar rats, which are scarcely reported. Blood smears from male Wistar rats (n = 120) and adult men were collected at room temperature. The integrity of Wright-stained cells was evaluated by an in silico image analysis from rat and human blood smear preserved with a toluene-based synthetic resin mounting medium. A single sample of human blood was used as a control of procedure. The reference intervals was established by cell counting. Based on the results of segmentation algorithm followed by an automatic thresholding analysis, the incorporation of resin favor the conservation of cell blood populations, and lead to identify morphologic features such as nucleus/cytoplasmic shape, granules presence and DNA appearance in nucleus of white blood cells. The use of a histological resin could favor a fast and efficient sample handling in silico MPBC measurements both in the species studied as in wild animals.

Pharmacological, Neurochemical, and Behavioral Mechanisms Underlying the Anxiolytic- and Antidepressant-like Effects of Flavonoid Chrysin.

Chrysin (5,7-dihydroxyflavone) is a flavonoid isolated from plants, such as Passiflora coerulea, Passiflora incarnata, and Matricaria chamomilla. This natural molecule exerts diverse pharmacological effects, which includes antioxidant, anti-inflammatory, anti-cancer, neuroprotective, and anti-apoptotic effects. Additionally, in brain structures, such as the hippocampus, prefrontal cortex, raphe nucleus, and striatum, involved in the physiopathology of anxiety and depression disorders, several neuropharmacological activities, including the activation of neurotransmitter systems (GABAergic, serotonergic, dopaminergic, and noradrenergic), neurotrophic factors, such as brain-derived neurotrophic factor and the nerve growth factor, and some signaling pathways are affected. The results showed that the anxiolytic and antidepressant-like effects of chrysin occurs through its interaction with specific neurotransmitter systems, principally the GABAergic and the serotonergic, and activation of other neurotrophic factors. However, it is not possible to discard the antioxidant and anti-inflammatory activities of chrysin while producing its anxiolytic- and antidepressant-like effects. Although these results have been obtained principally from pre-clinical research, they consistently demonstrate the potential therapeutic use of flavonoid chrysin as an anxiolytic and antidepressant agent. Therefore, this flavonoid could be considered as a promising novel therapy for anxiety and depression disorders.

HEMATOLOGIC REFERENCE INTEVALS FOR SPIDER MONKEYS (ATELES GEOFFROYI) IN MANAGED CARE WITH RESPECT TO SEX AND AGE.

The determination of health status in spider monkeys (Ateles geoffroyi) that are held in managed care requires periodic evaluation. The present study obtained baseline data on hematologic values, body weight, and length in A. geoffroyi. A total of 118 individuals from three housing centers were included in the study and grouped into two categories by age (92 adults, 26 juveniles) and sex (46 males, 72 females). Body weight, red blood cell (RBC) counts, and hemoglobin counts were significantly higher in adult males than in adult females. No differences in length were found between sex and age groups. The present findings indicate that hematologic values by age and sex in A. geoffroyi are similar to those reported in other spider monkey populations in both managed care and the wild. These results will be useful as a reference for young individuals and adults in future studies of the health of this species.

Estrous cycle modulates the anxiogenic effects of caffeine in the elevated plus maze and light/dark box in female rats.

Caffeine is a commonly used stimulant of the central nervous system that reduces fatigue, increases alertness, and exerts positive effects on emotion through actions on various brain structures. High doses of caffeine can cause headaches, heart palpitations, hyperactivity, and anxiety symptoms. Consequently, reducing the consumption of stimulant substances, such as sugar and caffeine, is proposed to ameliorate symptoms of premenstrual syndrome in women. The administration of steroid hormones has been suggested to modulate the effects of caffeine, but unknown is whether endogenous hormone variations during the estrous cycle modulate the pharmacological effects of caffeine. The present study evaluated the effects of caffeine (10, 20, and 40 mg/kg) during metestrus-diestrus and proestrus-estrus of the ovarian cycle in rats on anxiety-like behavior using the elevated plus maze and light/dark box. During metestrus-diestrus, all doses of caffeine increased anxiety-like behavior, indicated by the main variables in both behavioral tests (i.e., higher Anxiety Index and lower percent time spent on the open arms in the elevated plus maze and less time spent in the light compartment in the light/dark box). During proestrus-estrus, only 20 and 40 mg/kg caffeine increased these parameters of anxiety-like behavior, albeit only slightly. In conclusion, caffeine increased anxiety-like behaviors in metestrus-diestrus, with an attenuation of these effects of lower doses of caffeine in proestrus-estrus. These effects that were observed in metestrus-diestrus and proestrus-estrus may be associated with low and high concentrations of steroid hormones, respectively, that naturally occur during these phases of the ovarian cycle.

Association Between Socio-Affective Symptoms and Glutathione and CD4 and CD8 Lymphocytes in College Students.

Background: The prevalence of anxiety and depression in young students is associated with biosocial factors and scholastic stress. However, few studies have evaluated emotional-affective symptoms that are related to the immune system and antioxidant parameters in young individuals without diagnoses of affective disorders. Aim: This study aims to assess the relationship between emotional-affective symptoms and glutathione concentrations and CD4 and CD8 lymphocyte counts in college students. Methods: College students (n = 177) completed standardized psychometric instruments, including the Perceived Stress Scale, Hamilton Anxiety Scale, Beck Depression Inventory, Familiar Social and Friends Support Scale, and Rosenberg Scale. Blood samples were biochemically analyzed. Analyses of variance were conducted between four groups according to symptom severity. Results: A considerable prevalence of stress, anxiety, and depression symptoms was observed and negatively correlated with self-esteem and socio-familiar support. Perceived stress was sexually dimorphic. Although biochemical parameters were within reference ranges, glutathione, CD4, and CD8 tended to be lower in participants with anxiety and depression symptoms, which may be of predictive value. Conclusion: The relationship between antioxidant/immune parameters and socio-affective scores is latent in undiagnosed college students who might develop affective disorders. The findings suggest that during the initial development of affective disorders, stress management strategies should be implemented to help college students cope with the academic load and monitor negative changes in their physiological state.

GABA A /Benzodiazepine Receptor Complex in the Dorsal Hippocampus Mediates the Effects of Chrysin on Anxiety-Like Behaviour in Female Rats.

Systemic injections of the flavonoid chrysin (5,7-dihydroxyflavone) exert anxiolytic-like effects in ovariectomised and cycling female rats through actions on gamma-aminobutyric acid-A (GABA A ) receptors; however, it is unknown if chrysin directly acts on brain structures that are involved in regulating emotional processes, such as the hippocampus. The present study evaluated the effects of intrahippocampal microinjections of 0.25, 0.5, and 1 µg of chrysin on anxiety-like behaviour in the elevated plus maze (EPM) and locomotor activity test (LAT) in female rats in proestrus and dioestrus. Similar doses of the neurosteroid allopregnanolone were used as a reference GABAergic anxiolytic drug. The participation of the GABA A /benzodiazepine receptor complex was evaluated by administering the antagonists picrotoxin, bicuculline and flumazenil. In proestrus, 0.5 and 1 µg of chrysin and allopregnanolone induced anxiogenic-like behaviour. In dioestrus, chrysin, and allopregnanolone (0.5 µg) induced anxiolytic-like effects. Picrotoxin, bicuculline and flumazenil prevented the effects of chrysin and allopregnanolone in both proestrus and dioestrus. None of the treatments significantly affected locomotor activity. These results indicate that the GABA A /benzodiazepine receptor complex in the dorsal hippocampus regulates the effects of chrysin on anxiety-like behaviour, similar to the actions of allopregnanolone. The divergent effects of treatments across the oestrous cycle phases suggest complex interactions between GABA A receptors and compounds with an anxiolytic potential.

Chrysin reduces anxiety-like behavior through actions on GABAA receptors during metestrus-diestrus in the rat.

Low concentrations of ovarian hormones, among other factors, are associated with greater vulnerability to negative effects of environmental stressors and may trigger anxiety symptoms in females. The flavonoid chrysin (5,7-dihydroxyflavone) exerts anxiolytic-like effects in male and ovariectomized female rats, but it is unknown if chrysin could reduce anxiety-like behavior that naturally occurs through the ovarian cycle phases. The present study evaluated the effect of chrysin on anxiety-like behavior associated with the ovarian cycle phases in rats and the participation of γ-aminobutyric acid-A (GABAA) receptors in these actions. The acute effects of chrysin (2 mg/kg) were investigated in female cycling Wistar rats in the elevated plus maze, locomotor activity test, and light/dark test. Diazepam (2 mg/kg) was used as reference anxiolytic drug. The participation of GABAA receptor in the anxiolytic actions of chrysin was explored by pretreating the rats with the noncompetitive GABAA chloride ion channel antagonist picrotoxin (1 mg/kg). Chrysin and diazepam prevented anxiety-like behavior that was associated with the metestrus-diestrus phase in both the elevated plus maze and light/dark test, and these effects were reversed by picrotoxin, with no significant changes in spontaneous locomotor activity. No significant motor effects of chrysin were detected in either behavioral test during proestrus-estrus or metestrus-diestrus phases, whereas diazepam produced motor hypoactivity in the locomotor activity test during proestrus-estrus phase. These results indicate that the flavonoid chrysin prevents anxiety-like behavior that naturally occurs during metestrus-diestrus in two unconditioned models that are used to evaluate anxiety-like behavior, and these effects were mediated by actions on GABAA receptors.