Possible GABAergic mechanism in the protective effect of allopregnenolone against immobilization stress

Comparative evaluation of natural neuroprotectives and their combinations on chronic immobilization stress-induced depression in experimental mice

The present study evaluates the potential of neuroprotective phytochemicals-rutin (R), resveratrol (Res), 17β-estradiol (17β-E2), and their different combinations against chronic immobilization stress (CIS)-induced depression-like behaviour in male albino mice. Here, the mice were exposed to stress via immobilization of their four limbs under a restrainer for 6 h daily until 7 days of the induction after 30 min of respective drug treatment in different mice groups. The result found the protective effect of these phytoconstituents and their combinations against CIS-induced depression due to their ability to suppress oxidative stress, restore mitochondria, HPA-axis modulation, neurotransmitter level, stress hormones, and inflammatory markers. Also, the combination drug regimens of these phytoconstituents showed synergistic results in managing the physiological and biochemical features of depression. Thus, these neuroprotective could be utilized well in combination to manage depression-like symptoms during episodic stress. Furthermore, such results could be well justified when administered in polyherbal formulation with these neuroprotective as major components. In addition, an advanced study can be designed at the molecular and epigenetics level using a formulation based on these neuroprotective.

GABAA/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 (GABA_A) 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 GABA_A receptor in the anxiolytic actions of chrysin was explored by pretreating the rats with the noncompetitive GABA_A 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 GABA_A receptors.

To evaluate the anti-kindling effect of allopregnanolone alone and its interaction with sodium valporate in pentylenetetrazole induced kindling model

Background and purpose Studies in the animal models of epilepsy have suggested the anti-seizure effects of neuroactive steroids and its derivatives in kainic acid and pilocarpine induced limbic seizures and status epilepticus in mice, but no such studies have been reported in the published literature on the role of allopregnanolone in chemical kindling model and its interaction with sodium valproate. The purpose of this study was to evaluate the interaction between sodium valproate and allopregnanolone in pentylenetetrazole induced kindling model in rats.

Methods In a PTZ kindled Wistar rat model, sodium valproate and allopregnanolone were administered 30 min before the PTZ injection. The PTZ injection was given on alternate day till the animal became fully kindled or till 10 weeks. The parameters measured were latency to develop kindling and incidence of kindling, histopathological study of hippocampus, hippocampal anti-oxidant parameters and hippocampal DNA fragmentation studies.

Results In this study, the combination of low dose of allopregnanolone with low dose of sodium valproate showed a similar beneficial effect to that of a higher dose of sodium valproate in significantly reducing the number of kindled animals (0/8) as compare to PTZ control group (5/8) as well as the seizure scores and the histopathological scores. The combination significantly reduces oxidative stress by significantly decreasing the MDA levels, and increasing the SOD levels and GSH levels in the hippocampus of rats as compared to PTZ control group. So all these data suggest the antiepileptic effect of the combination and confers the synergistic interaction between the allopregnanolone and sodium valproate.

Conclusions It can be concluded that by choosing this combination the dose of sodium valproate can be reduced and thereby reduces the incidence of adverse effects caused by sodium valproate and hence proves to be a useful combination clinically. This study has lead the basis to further investigate the various combinations of neurosteroids and valproate in the process of epileptogenesis with better side effect profile.

Exogenous antioxidants--Double-edged swords in cellular redox state: Health beneficial effects at physiologic doses versus deleterious effects at high doses

The balance between oxidation and antioxidation is believed to be critical in maintaining healthy biological systems. Under physiological conditions, the human antioxidative defense system including e.g., superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH) and others, allows the elimination of excess reactive oxygen species (ROS) including, among others superoxide anions (O₂^.-), hydroxyl radicals (OH.), alkoxyl radicals (RO.) and peroxyradicals (ROO.). However, our endogenous antioxidant defense systems are incomplete without exogenous originating reducing compounds such as vitamin C, vitamin E, carotenoids and polyphenols, playing an essential role in many antioxidant mechanisms in living organisms. Therefore, there is continuous demand for exogenous antioxidants in order to prevent oxidative stress, representing a disequilibrium redox state in favor of oxidation. However, high doses of isolated compounds may be toxic, owing to prooxidative effects at high concentrations or their potential to react with beneficial concentrations of ROS normally present at physiological conditions that are required for optimal cellular functioning. This review aims to examine the double-edged effects of dietary originating antioxidants with a focus on the most abundant compounds, especially polyphenols, vitamin C, vitamin E and carotenoids. Different approaches to enrich our body with exogenous antioxidants such as via synthetic antioxidants, diets rich in fruits and vegetables and taking supplements will be reviewed and experimental and epidemiological evidences discussed, highlighting that antioxidants at physiological doses are generally safe, exhibiting interesting health beneficial effects.

The antioxidant potential of alprazolam on the redox status of peripheral blood leukocytes in restraint-stressed mice

AIMS

Stress can cause adverse reactions in the body that induce a wide range of biochemical and behavioral changes. Oxidative damage is an established outcome of stress that has been implicated in the pathogenesis of mood and anxiety disorders. Anxiolytic drugs are widely prescribed to treat these conditions; however, no animal study has investigated the effect of benzodiazepines on the levels of intracellular reactive oxygen species (ROS) in the peripheral blood leukocytes of stressed mice.

MAIN METHODS

Mice were immobilized for a period of 6h. Alprazolam (0.1-0.8 mg/kg of body weight) was administered 30 min before subjecting the animals to acute stress. The level of intracellular ROS in lymphocytes, granulocytes, and monocytes in the peripheral blood of stressed mice was investigated by using a 2',7'-dichlorofluorescein diacetate (DCFH-DA) probe.

KEY FINDINGS

Our results show that restraint stress significantly increases the generation of ROS in peripheral defense cells. Treatment with alprazolam partially reverses the adverse effects of stress.

SIGNIFICANCE

Our findings suggest that the therapeutic efficacy of alprazolam may be mediated, at least partially, by the reversal of oxidative damage as demonstrated by the protective enhancement of antioxidant status following a stress-induced decline. Because alprazolam is used for the treatment of anxiety in patients with cancer, neurodegenerative disease, inflammatory bowel diseases, and other diseases, these results may have important clinical implications.

Diazepam blocks striatal lipid peroxidation and improves stereotyped activity in a rat model of acute stress

In this work, the effect of a single dose of diazepam was tested on different markers of oxidative damage in the striatum of rats in an acute model of immobilization (restraint) stress. In addition, the locomotor activity was measured at the end of the restraint period. Immobilization was induced to animals for 24 hr, and then, lipid peroxidation, superoxide dismutase activity and content, and mitochondrial function were all estimated in striatal tissue samples. Corticosterone levels were measured in serum. Diazepam was given to rats as a pre-treatment (1 mg/kg, i.p.) 20 min. before the initiation of stress. Our results indicate that acute stress produced enhanced striatal levels of lipid peroxidation (73% above the control), decreased superoxide dismutase activity (54% below the control), reduced levels of mitochondrial function (35% below the control) and increased corticosterone serum levels (86% above the control). Pre-treatment of stressed rats with diazepam decreased the striatal lipid peroxidation levels (68% below the stress group) and improved mitochondrial function (18% above the stress group), but only mild preservation of superoxide dismutase activity was detected (17% above the stress group). In regard to the motor assessment, only the stereotyped activity was increased in the stress group with respect to control (46% above the control), and this effect was prevented by diazepam administration (30% below the stress group). The preventive actions of diazepam in this acute model of stress suggest that drugs exhibiting anxiolytic and antioxidant properties might be useful for the design of therapies against early acute phases of physic stress.

Early changes in oxidative stress markers in a rat model of acute stress: effect of l-carnitine on the striatum

This work focuses on the effect of acute stress on different markers of oxidative stress and mitochondrial dysfunction in the rat striatum. In addition, the effect of a single dose of l-carnitine (l-CAR, 300 mg/kg, i.p.) was evaluated in these animals. Immobilization (restraint) stress was induced to rats for 24 hr. The levels of lipid peroxidation (LP) and mitochondrial function (MF), as well as the superoxide dismutase (SOD) activity and content and reduced glutathione (GSH) levels, were all measured in striatal samples of animals subjected to stress. Our results indicate that acute stress is able to increase the striatal LP and reduced the levels of MF, while significantly lowered the manganese superoxide dismutase (Mn-SOD) activity. No changes were observed in the total striatal content of SOD, nor in GSH levels, but serum corticosterone content was increased by stress. l-CAR exhibited partial protective effects on the immobilized group, reducing the striatal LP and recovering the striatal MF and Mn-SOD activity. Our results suggest that acute restraint stress brings an accurate model for early pro-oxidant responses that can be targeted by broad-spectrum antioxidants like l-CAR.