Involvement of NO-cGMP pathway in anti-anxiety effect of aminoguanidine in stressed mice

A multi-modal approach to investigate Desmodium gangeticum's influence on stress-induced male infertility: In vivo, in vitro, and in silico assessments

Physical and psychological stress has an inverse relation with male libido and sperm quality. The present study investigates the potential fertility-enhancing properties of Desmodium gangeticum (DG) root extracts in male Wister rats subjected to immobilization-induced stress (SIMB). DG roots were extracted using n-hexane (HEDG), chloroform (CEDG), and water (AEDG). In the pilot study, aphrodisiac protentional was investigated at two doses (125 and 250 mg kg-1) of each extract. In the main study, the HEDG and AEDG at 125 and 250 mg kg-1 were challenged for the stress by immobilization (SIMB), for 6 h daily over 28 days. Parameters assessed included aphrodisiac effects, gonadosomatic index (GSI), semen quality, sperm quantity, fructose content, serum hormonal levels, testicular oxidative stress, and testicular histopathology. Additional in silico studies, including the lipid solubility index, molecular docking, molecular dynamics, and SymMap studies were conducted for validation. HEDG demonstrated significant aphrodisiac activity, improved - GSI, sperm quality and quantity, and fructose content, serum testosterone levels, histological changes induced by SIMB in the testes. Swiss ADME studies indicated Gangetin (a pterocarpan) had a high brain permeation index (4.81), a superior docking score (-8.22), and higher glide energy (-42.60), compared with tadalafil (-7.17). The 'Lig fit Prot' plot in molecular dynamics simulations revealed a strong alignment between Gangetin and phosphodiesterase type 5 (PDE5). HEDG exerts aphrodisiac effects by increasing blood testosterone levels and affecting PDE5 activity. The protective effects on spermatozoa-related parameters and testicular histological changes are attributed to the antioxidant and anti-inflammatory properties, of pterocarpan (gangetin).

The antidepressant-like effect of doxycycline is associated with decreased nitric oxide metabolite levels in the prefrontal cortex

Doxycycline is an antibiotic that has shown neuroprotective, anti-inflammatory, and antidepressant-like effects. Low doses of doxycycline revert the behavioral and neuroinflammatory responses induced by lipopolysaccharide treatment in a mice model of depression. However, the molecular mechanisms involved in the antidepressant action of doxycycline are not yet understood. Doxycycline inhibits the synthesis of nitric oxide (NO), which increases after stress exposure. Inducible NO synthase (iNOS) inhibition also causes antidepressant-like effects in animal models sensitive to antidepressant-like effects such as the forced swimming test (FST). However, no direct study has yet investigated if the antidepressant-like effects of doxycycline could involve changes in NO-mediated neurotransmission. Therefore, this study aimed at investigating: i) the behavioral effects induced by doxycycline alone or in association with ineffective doses of a NO donor (sodium nitroprusside, SNP) or an iNOS inhibitor (1400 W) in mice subjected to the FST; and ii) doxycycline effects in NO metabolite levels in the prefrontal cortex and hippocampus these animals. Male mice (8 weeks) received i.p. injection of saline or doxycycline (10, 30, and 50 mg/kg), alone or combined with SNP (0.1, 0.5, and 1 mg/kg) or 1400 W (1, 3, and 10 µg/kg), and 30 min later were submitted to the FST. Animals were sacrificed immediately after, and NO metabolites nitrate/nitrite (NOx) were measured in the prefrontal cortex and hippocampus. Doxycycline (50 mg/kg) reduced both the immobility time in the FST and NOx levels in the prefrontal cortex of mice compared to the saline group. The antidepressant-like effect of doxycycline in the FST was prevented by SNP (1 mg/kg) pretreatment. Additionally, sub-effective doses of doxycycline (30 mg/kg) associated with 1400 W (1 µg/kg) induced an antidepressant-like effect in the FST. Altogether, our data suggest that the reducing NO levels in the prefrontal cortex through inhibition of iNOS could be related to acute doxycycline treatment resulting in rapid antidepressant-like effects in mice.

"NO" Time in Fear Response: Possible Implication of Nitric-Oxide-Related Mechanisms in PTSD

Post-traumatic stress disorder (PTSD) is a psychiatric condition characterized by persistent fear responses and altered neurotransmitter functioning due to traumatic experiences. Stress predominantly affects glutamate, a neurotransmitter crucial for synaptic plasticity and memory formation. Activation of the N-Methyl-D-Aspartate glutamate receptors (NMDAR) can trigger the formation of a complex comprising postsynaptic density protein-95 (PSD95), the neuronal nitric oxide synthase (nNOS), and its adaptor protein (NOS1AP). This complex is pivotal in activating nNOS and nitric oxide (NO) production, which, in turn, activates downstream pathways that modulate neuronal signaling, including synaptic plasticity/transmission, inflammation, and cell death. The involvement of nNOS and NOS1AP in the susceptibility of PTSD and its comorbidities has been widely shown. Therefore, understanding the interplay between stress, fear, and NO is essential for comprehending the maintenance and progression of PTSD, since NO is involved in fear acquisition and extinction processes. Moreover, NO induces post-translational modifications (PTMs), including S-nitrosylation and nitration, which alter protein function and structure for intracellular signaling. Although evidence suggests that NO influences synaptic plasticity and memory processing, the specific role of PTMs in the pathophysiology of PTSD remains unclear. This review highlights pathways modulated by NO that could be relevant to stress and PTSD.

Behavioral and Proteomic Studies Reveal Methylglyoxal Activate Pathways Associated with Alzheimer's Disease

Diabetes is one of the major risk factors for Alzheimer's disease (AD) development. The role of elevated levels of glucose, methylglyoxal (MGO), and advanced glycation end products (AGEs) in the pathogenesis of AD is not well understood. In this pursuit, we studied the role of methylglyoxal in the pathogenesis of AD in rat models. The elevated plus-maze (EPM) behavioral study indicated that MGO induces anxiety. Treatment of telmisartan (RAGE expression inhibitor) and aminoguanidine (MGO quencher) attenuated MGO induced anxiety. Further, hippocampal proteomics demonstrated that MGO treated rats differentially regulate proteins involved in calcium homeostasis, mitochondrial functioning, and apoptosis, which may affect neurotransmission and neuronal plasticity. The hippocampal tau phosphorylation level was increased in MGO treated rats, which was reduced in the presence of aminoguanidine and telmisartan. The plasma fructosamine level was increased upon MGO treatment. Hippocampal histochemistry showed vascular degeneration and neuronal loss upon MGO treatment. This study provides mechanistic insight into the role of MGO in the diabetes-associated development of AD.

Nitric Oxide Synthase inhibition counteracts the stress-induced DNA methyltransferase 3b expression in the hippocampus of rats

It has been postulated that the activation of NMDA receptors (NMDAr) and nitric oxide (NO) production in the hippocampus is involved in the behavioral consequences of stress. Stress triggers NMDAr-induced calcium influx in limbic areas, such as the hippocampus, which in turn activates neuronal NO synthase (nNOS). Inhibition of nNOS or NMDAr activity can prevent stress-induced effects in animal models, but the molecular mechanisms behind this effect are still unclear. In this study, cultured hippocampal neurons treated with NMDA or dexamethasone showed an increased of DNA methyltransferase 3b (DNMT3b) mRNA expression, which was blocked by pre-treatment with nNOS inhibitor nω -propyl-l-arginine (NPA). In rats submitted to the Learned Helplessness paradigm (LH), we observed that inescapable stress increased DNMT3b mRNA expression at 1h and 24h in the hippocampus. The NOS inhibitors 7-NI and aminoguanidine (AMG) decreased the number of escape failures in LH and counteracted the changes in hippocampal DNMT3b mRNA induced in this behavioral paradigm. Altogether, our data suggest that NO produced in response to NMDAr activation following stress upregulates DNMT3b in the hippocampus.

Phosphodiesterase-5 Inhibitor Attenuates Anxious Phenotypes and Movement Disorder Induced by Mild Ischemic Stroke in Rats

Objective

Patients with mild ischemic stroke experience various sequela and residual symptoms, such as anxious behavior and deficits in movement. Few approaches have been proved to be effective and safe therapeutic approaches for patients with mild ischemic stroke by acute stroke. Sildenafil (SIL), a phosphodiesterase-5 inhibitor (PDE5i), is a known remedy for neurodegenerative disorders and vascular dementia through its angiogenesis and neurogenesis effects. In this study, we investigated the efficacy of PDE5i in the emotional and behavioral abnormalities in rats with mild ischemic stroke.

Methods

We divided the rats into four groups as follows (n=20, respectively) : group 1, naïve; group 2, middle cerebral artery occlusion (MCAo30); group 3, MCAo30+SIL-pre; and group 4, MCAo30+SIL-post. In the case of drug administration groups, single dose of PDE5i (sildenafil citrate, 20 mg/kg) was given at 30-minute before and after reperfusion of MCAo in rats. After surgery, we investigated and confirmed the therapeutic effect of sildenafil on histology, immunofluorescence, behavioral assays and neural oscillations.

Results

Sildenafil alleviated a neuronal loss and reduced the infarction volume. And results of behavior task and immunofluorescence shown possibility that anti-inflammation process and improve motor deficits sildenafil treatment after mild ischemic stroke. Furthermore, sildenafil treatment attenuated the alteration of theta-frequency rhythm in the CA1 region of the hippocampus, a known neural oscillatory marker for anxiety disorder in rodents, induced by mild ischemic stroke.

Conclusion

PDE5i as effective therapeutic agents for anxiety and movement disorders and provide robust preclinical evidence to support the development and use of PDE5i for the treatment of mild ischemic stroke residual disorders.

Low doses of ketamine and guanosine abrogate corticosterone-induced anxiety-related behavior, but not disturbances in the hippocampal NLRP3 inflammasome pathway

RATIONALE

Guanosine has been shown to potentiate ketamine's antidepressant-like actions, although its ability to augment the anxiolytic effect of ketamine remains to be determined.

OBJECTIVE

This study investigated the anxiolytic-like effects of a single administration with low doses of ketamine and/or guanosine in mice subjected to chronic administration of corticosterone and the role of NLRP3-driven signaling.

METHODS

Corticosterone (20 mg/kg, p.o.) was administered for 21 days, followed by a single administration of ketamine (0.1 mg/kg, i.p.), guanosine (0.01 mg/kg, p.o.), or ketamine (0.1 mg/kg, i.p.) plus guanosine (0.01 mg/kg, p.o.). Anxiety-like behavior and NLRP3-related targets were analyzed 24 h following treatments.

RESULTS

Corticosterone reduced the time spent in the open arms and the central zone in the elevated plus-maze test and open-field test, respectively. Corticosterone raised the number of unsupported rearings and the number and time of grooming, and decreased the latency to start grooming in the open-field test. Disturbances in regional distribution (increased rostral grooming) and grooming transitions (increased aborted and total incorrect transitions) were detected in corticosterone-treated mice. These behavioral alterations were accompanied by increased immunocontent of Iba-1, ASC, NLRP3, caspase-1, TXNIP, and IL-1β in the hippocampus, but not in the prefrontal cortex. The treatments with ketamine, guanosine, and ketamine plus guanosine were effective to counteract corticosterone-induced anxiety-like phenotype, but not disturbances in the hippocampal NLRP3 pathway.

CONCLUSIONS

Our study provides novel evidence that low doses of ketamine and/or guanosine reverse corticosterone-induced anxiety-like behavior and shows that the NLRP3 inflammasome pathway is likely unrelated to this response.

Auraptene exerts protective effects on maternal separation stress-induced changes in behavior, hippocampus, heart and serum of mice

Early life stress is associated with various complications. Auraptene has significant antioxidant and anti-inflammatory effects. This study aimed to assess the probable underlying mechanisms that mediate changes in the behavior, hippocampus, heart and serum in the mouse model of maternal separation (MS) stress. We evaluated the possible protective effects of auraptene in these changes focusing on inflammatory response and oxidative state. Mice were treated with auraptene (5, 10, and 50 mg/kg). In addition, anxiety-like behaviors were evaluated using behavioral tests; including open field test (OFT) and elevated plus maze (EPM). Hippocampus and heart samples were assessed histopathologically. Levels of malondialdehyde (MDA) and antioxidant capacity, as well as nitrite levels, were measured in serum, heart, and hippocampal tissues. Moreover, gene expression of inflammatory markers (Il-1β and Tlr-4) was evaluated in the heart and hippocampus. Results showed that auraptene reversed the negative effects of MS on behavior (increased time spent in central zone of the OFT and time and entries to the open arms of the EPM). Auraptene mitigated adverse effects of MS on the hippocampus (increased diameter and decreased percentage of dark neurons in the CA3 area). Accordingly, auraptene decreased MDA and nitrite levels and increased the antioxidant capacity in serum, and hippocampal samples. However, we observed different effects for different doses of auraptene in the heart samples. We concluded that MS is associated with anxiety-like behavior and cellular/molecular modifications in the heart, hippocampus and serum. We found that auraptene exerted protective effects against these negative effects of MS in mouse.

Involvement of GABAergic and nitrergic systems in the anxiolytic and hypnotic effects of Curcuma longa: its interaction with anxiolytic-hypnotics

OBJECTIVES

Concurrent use of herbs with drugs have become a major healthcare problem. Herb-drug interactions could lead to therapeutic failure or toxicity. Hence, this study seeks to evaluate the impact of combining Curcuma longa rhizome (CL) with selected anxiolytic and hypnotic drugs.

METHODS

CL (100, 200 or 400 mg/kg, p.o.) was administered to mice 1 h before subjecting the animals to elevated plus maze (EPM), hole board test (HBT), open field test (OFT) and rotarod test for anxiolytic-like effect as well as hexobarbitone-induced sleeping time (HIST) for hypnotic activity. The involvement of GABAergic and nitrergic systems in CL-induced anxiolytic and hypnotic actions were also evaluated. The effect of concurrent use of CL with midazolam, imipramine, nifedipine, propranolol and carbamazepine were evaluated in anxiolytic-hypnosis models.

RESULTS

The peak anxiolytic-like effect of CL was obtained at 400 mg/kg in the EPM and hole-board test without affecting muscle coordination in the rotarod test while the peak hypnosis-potentiation was observed at 100 mg/kg. CL-induced anxiolytic-hypnotic-like effects were reversed by the pretreatment of mice with flumazenil or NG-nitro-l-arginine.

CONCLUSIONS

Curcuma longa possesses anxiolytic and hypnotic effects through its interaction with GABAergic and nitrergic systems. Conversely, co-administration of C. longa with midazolam potentiate barbiturate-induced hypnosis.

The impact of phosphodiesterase-5 inhibitor (sildenafil citrate) on some hippocampal neurotransmitters, oxidative stress status, minerals, and anxiety-like behavior in rats

Objective:

The purpose of this work was to investigate the effect of phosphodiesterase type 5 (PDE-5) inhibitor sildenafil citrate (SC) on the level of brain hippocampal neurophysiological parameters (inhibitory and excitatory neurotransmitters), oxidant/antioxidant status, minerals, and anxiety-like behavior using albino male rats.

Materials and methods:

A total of 24 albino male rats were allocated to three separate groups (each one had eight rats): control and SC 5 and 10 mg/kg treatments via i.p. infusion every 3 days for 12 injections. For the behavior of anxiety evaluation, the elevated plus maze test was conducted 1 day after the last treatment, and then all the rats were killed. For serum separation, the blood samples were taken, and hippocampus was dissected from the brain and stored frozen until analysis.

Results:

Both doses of sildenafil significantly improved brain hippocampal neurotransmitter [norepinephrine, serotonin (5-hydroxytryptamine), and gamma-aminobutyric acid] values accompanied by a decreased dopamine level. Interestingly, the SC higher given dose (10 mg/kg) increased the malondialdehyde level with the reduction of the antioxidant parameters [reduced glutathione (GSH) level, catalase (CAT), and superoxide dismutase (SOD) activities] although the lower dose of SC did not cause oxidative stress. Serum and brain hippocampal K, Cu, and Se concentrations were also increased with SC treatments. Moreover, the test of elevated plus maze revealed an anxiolytic impact of sildenafil.

Conclusion:

It was concluded that SC improved the parameters of some hippocampal neurotransmitters and minerals accompanied by anxiolytic impact with the test of elevated plus maze, with a state of oxidative stress revealed with the higher dose of SC which was not recorded with the lower dose.

NOS-2 participates in the behavioral effects of ethanol withdrawal in zebrafish

Nitric oxide has been implicated in symptoms of ethanol withdrawal in animal models. Zebrafish have been used as models to study neurobehavioral effects of ethanol (EtOH) withdrawal, but the mechanisms associated with these effects are not yet clear. Adult zebrafish were treated with 1% EtOH for 20 min per day for 8 days, injected with the nitric oxide synthase 2 (NOS-2) inhibitor aminoguanidine (50 mg/kg), and allowed to experience withdrawal (WD) in their hometanks for 7 days. EtOH WD increased anxiety-like behavior in the novel tank test, an effect that was blocked by aminoguanidine. EtOH WD also increased brain levels of nitrite, an effect that was partially blocked by aminoguanidine. These results underline a novel mechanism by which NOS-2 controls anxiety-like responses to ethanol withdrawal, with implications for the mechanistic study of symptoms associated with chronic ethanol abuse. Preprint: https://dx.doi.org/10.20944/preprints201912.0219.v1 Data and scripts: https://github.com/lanec-unifesspa/etoh-withdrawal/tree/master/NOS2.

Sucrose and saccharin differentially modulate depression and anxiety-like behavior in diabetic mice: exposures and withdrawal effects

RATIONALE

Sugar has addictive potential owing to increase in monoaminergic-transmission at pleasure and reward centers of brain. Insulin dysfunction triggered synaptic monoamine deficit is associated with sugar overeating and craving-related psychological changes in diabetic patients. Sugar-substitute (saccharin) is non-caloric artificial sweetener that may alleviate brain disorders in diabetes.

OBJECTIVES

In present study, effects of sucrose and sugar-substitute (saccharin) exposures and withdrawal on depression and anxiety-like behavior in type 2 diabetic mice were assessed.

METHODS

Swiss albino mice were injected with streptozotocin (135 mg/kg). After induction of diabetes, mice were exposed to a two-bottle water-water, 10% sucrose-water, or 10% saccharin-water choice paradigm for 28 days. Separate groups were employed to assess withdrawal effect of sucrose or saccharin in diabetic mice. Monoamine oxidase (MAO), corticosterone, thiobarbituric acid reactive substances (TBARS), and reduced glutathione (GSH) were quantified after behavioral tests.

RESULTS

Diabetic mice manifested preference towards 10% sucrose or saccharin over water. Sucrose-overeating by diabetic mice amplified symptoms of depression and anxiety; however, withdrawal further exaggerated these behavioral abnormalities. Substitution of sucrose by 10% saccharin attenuated the depressive and anxiety-like behavior in comparison to diabetic mice that were exposed separately to water-water or sucrose-water alone, and with respect to normal mice. Although withdrawal from saccharin resurfaced behavioral anomalies in diabetic mice, however, these were significantly low in comparison with withdrawal from sucrose or normal group. Reinstatement of exposure to saccharin mitigated symptoms of depression and anxiety in diabetic mice.

CONCLUSION

Preference of sucrose overeating augments while saccharin mitigates depressive and anxiety behavior during diabetes.

Nitrergic signaling modulation by ascorbic acid treatment is responsible for anxiolysis in mouse model of anxiety

The present study was designed to investigate the effect of ascorbic acid (AA) treatment on the anxiety related behavioral and neurochemical alterations. AA (50, 100 and 200 mg/kg, i.p.) was administered to the mice and anxiety related behavior and levels of glutamate and nitrite in the brain of mice were determined. The results obtained revealed that the administration of AA (100 mg/kg, i.p.) significantly reduced the anxiety related behavior and the levels of nitrite in the brain of mice. Nitrergic interactions were further determined by the pretreatment of mice with nitric oxide (NO) modulator and AA treatment followed by behavioral and neurochemical measurements. The results obtained suggested that NO inhibition potentiated the anxiolytic like activity of AA in mice. It was also observed that the glutamate and nitrite level in the brain of mice were significantly reduced by the NO inhibitor pretreatment. Thus, the present study demonstrated the possible nitrergic pathways modulation in the anxiolytic like activity of AA in mice.

Nitric oxide signalling and antidepressant action revisited

Studies about the pathogenesis of mood disorders have consistently shown that multiple factors, including genetic and environmental, play a crucial role on their development and neurobiology. Multiple pathological theories have been proposed, of which several ultimately affects or is a consequence of dysfunction in brain neuroplasticity and homeostatic mechanisms. However, current clinical available pharmacological intervention, which is predominantly monoamine-based, suffers from a partial and lacking response even after weeks of continuous treatment. These issues raise the need for better understanding of aetiologies and brain abnormalities in depression, as well as developing novel treatment strategies. Nitric oxide (NO) is a gaseous unconventional neurotransmitter, which regulates and governs several important physiological functions in the central nervous system, including processes, which can be associated with the development of mood disorders. This review will present general aspects of the NO system in depression, highlighting potential targets that may be utilized and further explored as novel therapeutic targets in the future pharmacotherapy of depression. In particular, the review will link the importance of neuroplasticity mechanisms governed by NO to a possible molecular basis for the antidepressant effects.

Amelioration of neurodegeneration and cognitive impairment by Lemon oil in experimental model of Stressed mice

Citrous lemon (Rutaceae) an Indian folk medicine has been used for the treatment of various pathological diseases viz., diabetes, cardiovascular, inflammation, hepatobiliary dysfunction and neurodegenerative disorder. Can lemon oil altered the memory of unstressed and stressed mice, a basic question for which the present work was put on trial. The present investigation was intended to assess the impact of Lemon oil on memory of unstressed and Stressed Swiss young Albino mice. Lemon oil (50 and 100 mg/kg o.r.) and donepezil (10 mg/kg) were guided for three weeks to different groups of stressed and unstressed mice. The nootropic movement was assessed utilizing elevated plus maze and Hebbs Williams Maze. Cerebrum acetylcholinesterase (AChE), plasmacorticosterone, decreased glutathione, lipid per oxidation alongside superoxide dismutase and catalase was surveyed as marker for disease. Histopathology was performed for estimation of drug effects. Acute immobilized stress was induce, lemon oil (100 mg/kg) and donepezil together indicated memory enhancing movement both in stressed and unstressed mice. Lemon oil significantly (p < 0.001) altered and lowered brain AChE activity both in stressed and unstressed mice. Scopolamine induced amnesia was also significantly altered and reversed both in stressed and unstressed mice by lemon oil at a dose of 50 and 100 mg/kg. Lemon oil (50 and 100 mg/kg) was further able to control the corticosterone level in plasma for stressed mice. Lemon oil significantly (p < 0.001) elevated the level of catalase, superoxide dismutase and reduced glutathione levels both in stressed and unstressed animals with respect to controlled group along with TBARS both in stressed and unstressed compared with control group. Hence it can be concluded that memory enhancing activity might be related to reduction in AChE and TBARS activity and by elevated GSH, SOD and catalase through decrease in raised plasma corticosterone levels.

Agmatine attenuates chronic unpredictable mild stress-induced anxiety, depression-like behaviours and cognitive impairment by modulating nitrergic signalling pathway

Agmatine, a neurotransmitter/neuromodulator, has shown to exert numerous effects on the CNS. Chronic stress is a risk factor for development of depression, anxiety and deterioration of cognitive performance. Compelling evidences indicate an involvement of nitric oxide (NO) pathway in these disorders. Hence, investigation of the beneficial effects of agmatine on chronic unpredictable mild stress (CUMS)-induced depression, anxiety and cognitive performance with the involvement of nitrergic pathway was undertaken. Mice were subjected to a battery of stressors for 28days. Agmatine (20 and 40mg/kg, i.p.) alone and in combination with NO modulators like L-NAME (15mg/kg, i.p.) and l-arginine (400mg/kg i.p.) were administered daily. The results showed that 4-weeks CUMS produces significant depression and anxiety-like behaviour. Stressed mice have also shown a significant high serum corticosterone (CORT) and low BDNF level. Chronic treatment with agmatine produced significant antidepressant-like behaviour in forced swim test (FST) and sucrose preference test, whereas, anxiolytic-like behaviour in elevated plus maze (EPM) and open field test (OFT) with improved cognitive impairment in Morris water maze (MWM). Furthermore, agmatine administration reduced the levels of acetylcholinesterase and oxidative stress markers. In addition, agmatine treatment significantly increased the BDNF level and inhibited serum CORT level in stressed mice. Treatment with L-NAME (15mg/kg) potentiated the effect of agmatine whereas l-arginine abolished the anxiolytic, antidepressant and neuroprotective effects of agmatine. Agmatine showed marked effect on depression and anxiety-like behaviour in mice through nitrergic pathway, which may be related to modulation of oxidative-nitrergic stress, CORT and BDNF levels.

Salivary Nitric Oxide, a Biomarker for Stress and Anxiety?

OBJECTIVE

To investigate if salivary nitrate correlates to the daily psychological stress and anxiety in a group of human subjects.

METHODS

The convenient sample recruitment method was employed; data from seventy three subjects were analyzed. The Perceived Stress Scale (PSS) and Hamilton Anxiety Rating Scale (HAM-A) inventories were used to determine stress and anxiety scores respectively. Salivary nitric oxide was measured through nitrate (NOx) levels using the Griess reaction method.

RESULTS

Although stress and anxiety were correlated. No significant correlation exists between salivary nitrate and daily psychological stress and anxiety in the study's participants.

CONCLUSION

While all previous studies focused NOx levels in acute stress models. This is the first study to investigate the correlation between salivary nitrates and daily psychological stress and anxiety. Although stress and anxiety were correlated, there is no correlation between salivary nitrates and daily psychological stress and anxiety. Further studies are required to investigate this correlation using other biological samples such as plasma.

Neuroprotective effects of Nigella sativa extracts during germination on central nervous system

Background:

Nigella sativa Linn. which has many acclaimed medicinal properties is an indigenous herbaceous plant and belongs to the Ranunculaceae family, which grows in countries bordering the Mediterranean Sea, Pakistan and India.

Objective:

This study was designed to investigate the effects of N. sativa seed extracts of different germination phases on the central nervous system (CNS) responses in experimental animals.

Materials and Methods:

Anxiolytic, locomotor activity of extracts (1 g/kg of body weight) was evaluated in both stressed and unstressed animal models and antiepileptic effect was evaluated by maximal electroshock seizure model keeping diazepam (20 mg/kg) as a positive control. Antidepressant effect was evaluated by forced swim test and tail suspension test keeping imipramine (15 mg/kg) as a positive control.

Results:

All tested extracts of N. sativa during different phases of germination (especially 5^th day germination phase) showed significant (P < 0.001) anxiolytic effect in comparison to control. Diazepam reduced locomotor activity in control (unstressed) rats but did not show affect in stressed rats while N. sativa extracts from germination phases significantly (P < 0.001) reduced locomotor activity in unstressed as well as stressed animals. All the extracts of N. sativa from different germination phases exhibited significant (P < 0.001) reduction in various phases of epileptic seizure on comparison with the reference standard (diazepam). During antidepressant test, N. sativa extracts exhibited a slight reduction in the immobility of rats.

Conclusion:

During germination, especially in 5^th day germination extract, N. sativa showed significant CNS depressant activity as compared to whole seeds that possibly may be due higher content of secondary metabolites produced during germination.

Increased Contextual Fear Conditioning in iNOS Knockout Mice: Additional Evidence for the Involvement of Nitric Oxide in Stress-Related Disorders and Contribution of the Endocannabinoid System

BACKGROUND

Inducible or neuronal nitric oxide synthase gene deletion increases or decreases anxiety-like behavior in mice, respectively. Since nitric oxide and endocannabinoids interact to modulate defensive behavior, the former effect could involve a compensatory increase in basal brain nitric oxide synthase activity and/or changes in the endocannabinoid system. Thus, we investigated the expression and extinction of contextual fear conditioning of inducible nitric oxide knockout mice and possible involvement of endocannabinoids in these responses.

METHODS

We evaluated the effects of a preferential neuronal nitric oxide synthase inhibitor, 7-nitroindazol, nitric oxide synthase activity, and mRNA changes of nitrergic and endocannabinoid systems components in the medial prefrontal cortex and hippocampus of wild-type and knockout mice. The effects of URB597, an inhibitor of the fatty acid amide hydrolase enzyme, which metabolizes the endocannabinoid anandamide, WIN55,212-2, a nonselective cannabinoid agonist, and AM281, a selective CB1 antagonist, on contextual fear conditioning were also evaluated.

RESULTS

Contextual fear conditioning expression was similar in wild-type and knockout mice, but the latter presented extinction deficits and increased basal nitric oxide synthase activity in the medial prefrontal cortex. 7-Nitroindazol decreased fear expression and facilitated extinction in wild-type and knockout mice. URB597 decreased fear expression in wild-type and facilitated extinction in knockout mice, whereas WIN55,212-2 and AM281 increased it in wild-type mice. Nonconditioned knockout mice showed changes in the mRNA expression of nitrergic and endocannabinoid system components in the medial prefrontal cortex and hippocampus that were modified by fear conditioning.

CONCLUSION

These data reinforce the involvement of the nitric oxide and endocannabinoids (anandamide) in stress-related disorders and point to a deregulation of the endocannabinoid system in situations where nitric oxide signaling is increased.

Possible involvement of GABAergic and nitriergic systems for antianxiety-like activity of piperine in unstressed and stressed mice

BACKGROUND

An investigation was made to explore the possibility of anxiolytic activity of piperine in unstressed and stressed mice along with the underlying role of nitriergic and GABAergic modulation for the noted activity of piperine.

METHODS

Piperine (5, 10 and 20mg/kg, ip) was administered to unstressed mice. In another groups of animals, piperine was administered 30 min before subjecting them to immobilization stress for 6h. Antianxiety activity was evaluated by employing elevated plus maze, light-dark box and social interaction test. Diazepam was employed as standard anxiolytic drug.

RESULTS

Piperine produced significant antianxiety-like activity in unstressed and stressed mice. The anxiolytic-like activity of piperine was comparable to diazepam. In unstressed mice, piperine significantly increased brain GABA levels, but could not produce any change in plasma nitrite levels. Meanwhile, in stressed mice, piperine did not produce any significant change in GABA levels, but significantly decreased nitrite levels. Pre-treatment with aminoguanidine (50mg/kg, ip), an inducible nitric oxide synthase (NOS) inhibitor, significantly potentiated the anxiolytic-like activity of piperine, as compared to piperine and aminoguanidine alone in stressed mice. On the other hand, pretreatment with 7-nitroindazole (20mg/kg, ip), a neuronal NOS inhibitor significantly potentiated the antianxiety-like activity of piperine, as compared to piperine and 7-nitroindazole alone in unstressed mice.

CONCLUSION

These data suggest that the piperine produced significant anxiolytic activity in unstressed mice possibly through increase in GABA levels and inhibition of neuronal NOS. On the other hand, antianxiety activity in stressed mice might be through inhibition of inducible NOS.

Sildenafil enhances locomotor activity in young mice and exerts anxiogenic effects in both young and aged mice

Background

Sildenafil is a selective PDE5 inhibitor that increases cGMP levels in the target tissues and is an effective treatment agent for erectile dysfunction. The nitric oxide-cGMP pathway might be implicated in regulation of certain CNS functions, including locomotor activity and anxiety.

Material/Methods

The aim of the current study was to investigate effects of sildenafil (3 and 10 mg/kg) on anxiety and locomotor activity in open field and elevated plus maze (EPM) tests in young and aged mice.

Results

Sildenafil (3 and 10 mg/kg) significantly decreased the percent of time spent in the open arms compared to the control group in young animals in the EPM test, but only the 10 mg/kg dose significantly decreased the percentage of total number of entries to the open arms in young animals. Sildenafil (3 and 10 mg/kg) significantly decreased the percentage of total number of entries to the open arms in aged animals in the EPM test, but it significantly increased total distance moved and speed of the animals in the locomotor activity test in young animals. The total distance moved and the speed of the animals significantly decreased in aged animals compared to the young control group, although sildenafil (3 and 10 mg/kg) did not alter these parameters in aged mice.

Conclusions

Our results show that sildenafil had anxiogenic effects in young as well as aged mice, but it enhanced locomotor activity only in the young mice in the EPM test. Thus, sildenafil seems to exert different effects on anxiety and locomotion in young and aged animals.

Chronic treatment with the phosphodiesterase type 5 inhibitors sildenafil and tadalafil display anxiolytic effects in Flinders Sensitive Line rats

There are conflicting results from behavioural studies regarding whether the activation or inhibition of the cGMP-nitric oxide (NO) pathway induces anxiolytic-like behaviour. Sildenafil, an inhibitor of cGMP-selective phosphodiesterase-5, increases anxiety acutely, but previous evidence suggests that its chronic administration may be anxiolytic, and could involve a cholinergic interaction. We used the Flinders Sensitive Line (FSL) rat, a genetic model of depression that presents with increased anxiety- and depression-like behaviour, to investigate the action of chronic treatment with the PDE5 inhibitors sildenafil or tadalafil, with/without atropine on social interaction behaviour, a correlate for anxiety. Fluoxetine was used as positive control, with validation performed using Flinders Resistant Line (FRL) rats. In order to relate behavioural changes to brain penetration, we determined the concentration of sildenafil in cortex and hippocampus of rats following the schedule above using LC-MS/MS. FSL rats displayed significantly reduced social interactive behaviour than FRL rats, while sildenafil, tadalafil, and fluoxetine significantly reversed these deficits. Atropine did not exert effects on social interactive behaviour, nor did it modulate the effects of sildenafil or tadalafil. Sildenafil was present in cortex and hippocampus regions in lower nanomolar concentrations after chronic treatment, in agreement with the binding to PDE5 required for pharmacological effects. This study emphasizes the complicated regulation of anxiety by the cGMP-NO system, and provides supporting evidence for an anxiolytic action after the chronic activation of this pathway. As far as we know this is also the first report to formally demonstrate that sildenafil effectively crosses the blood-brain barrier to elicit central effects.

Thymoquinone produced antianxiety-like effects in mice through modulation of GABA and NO levels

The aim of the present study was to investigate the role of GABAergic and nitriergic modulation in the antianxiety effect of thymoquinone, a major constituent of Nigella sativa, in mice under unstressed and stressed conditions. Thymoquinone (10 and 20 mg/kg), methylene blue (1 mg/kg) and diazepam (2 mg/kg) were administered followed by behavioral testing using an elevated plus maze, the light/dark test and the social interaction test in both unstressed and stressed mice (mice subjected to 6 h immobilization). The effects of the above-mentioned drugs on plasma nitrite, a stable metabolite of nitric oxide (NO) and brain GABA content were also studied. Diazepam (2 mg/kg) produced significant anxiolytic-like effects only in unstressed mice. However, diazepam significantly increased the GABA content in both unstressed and stressed mice as compared with their respective control groups. Thymoquinone (10 and 20 mg/kg) produced significant antianxiety effects in unstressed mice without altering nitrite levels, but only the higher dose (20 mg/kg) of thymoquinone increased the GABA content in unstressed mice. In stressed mice, thymoquinone (20 mg/kg) showed anxiolytic effects, with a significant decrease in plasma nitrite and reversal of the decreased brain GABA content. Pre-treatment with methylene blue enhanced the antianxiety effect of thymoquinone in both unstressed and stressed mice. Therefore, the present study suggests an involvement of NO-cGMP and GABAergic pathways in the anxiolytic-like activity of thymoquinone.

Inhibition of iNOS induces antidepressant-like effects in mice: pharmacological and genetic evidence

Recent evidence has suggested that systemic administration of non-selective NOS inhibitors induces antidepressant-like effects in animal models. However, the precise involvement of the different NOS isoforms (neuronal-nNOS and inducible-iNOS) in these effects has not been clearly defined yet. Considering that mediators of the inflammatory response, that are able to induce iNOS expression, can be increased by exposure to stress, the aim of the present study was to investigate iNOS involvement in stress-induced behavioral consequences in the forced swimming test (FST), an animal model sensitive to antidepressant drugs. Therefore, we investigated the effects induced by systemic injection of aminoguanidine (preferential iNOS inhibitor), 1400W (selective iNOS inhibitor) or n-propyl-l-arginine (NPA, selective nNOS inhibitor) in mice submitted to the FST. We also investigated the behavior of mice with genetic deletion of iNOS (knockout) submitted to the FST. Aminoguanidine significantly decreased the immobility time (IT) in the FST. 1400W but not NPA, when administered at equivalent doses considering the magnitude of their Ki values for iNOS and nNOS, respectively, reduced the IT, thus suggesting that aminoguanidine-induced effects would be due to selective iNOS inhibition. Similarly, iNOS KO presented decreased IT in the FST when compared to wild-type mice. These results are the first to show that selective inhibition of iNOS or its knockdown induces antidepressant-like effects, therefore suggesting that iNOS-mediated NO synthesis is involved in the modulation of stress-induced behavioral consequences. Moreover, they further support NO involvement in the neurobiology of depression. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Brain homeostasis is maintained by "danger" signals stimulating a supportive immune response within the brain's borders

An organism's behavior is determined by the way it senses and perceives the surrounding environment, and by its responses to these stimuli. The major factors known to affect the behavioral response to an event are genetic background, environmental factors, and past experiences, and their imprinting on the relevant brain circuits. Recently, circulating immune cells were introduced as novel players into this system. It was proposed that the brain and circulating immune cells engage in a continuous dialogue that takes place within the brain's territory, though outside the parenchyma (occurring within the brain's borders - the choroid plexi, the brain meninges and the cerebrospinal fluid (CSF)). The cytokines secreted by activated leukocytes residing at the borders were shown to affect neurotrophic factors production within the parenchyma. Here, we suggest that such a dialogue is stimulated at the brain's borders, upon need, by a "danger" signal that originates in the parenchyma in response to any destabilizing event, and discuss the potential role of reactive oxygen species (ROS) in transmitting this signal. Accordingly, a failure to restore balance is likely to lead to aberrant responses to subsequent events. This view thus supports the contention that circulating immune cells are required to maintain the brain's balanced activity and suggests a novel mechanism whereby the surveying immune cells are sensing the brain's status and needs.

Possible underlying influence of p38MAPK and NF-κB in the diminished anti-anxiety effect of diazepam in stressed mice

The present study was designed to explore the possible nitriergic influence and role of p38MAPK and NF-κB in the diminished anti-anxiety effect of diazepam in stressed mice, using the elevated plus maze and light/dark box to assess anxiety. Immobilization stress for 6 h enhanced an anxiety-like behavior and increased plasma nitrite levels in mice. Diazepam (2 mg/kg, i.p.) produced an anti-anxiety effect in unstressed mice, but could not produce any change in anxiety levels of stressed mice. SB-203580 (2 mg/kg, i.p.), a specific inhibitor of p38MAPK, per se produced a significant antianxiety-like activity in stressed mice. Administration of a combination of SB-203580 (2 mg/kg, i.p.) and diazepam (2 mg/kg) in stressed mice produced a significantly higher antianxiety-like activity than that produced by SB-203580 alone. Pyrrolidine dithiocarbamate (PDTC), an inhibitor of the activation of NF-κB, per se produced a significant antianxiety-like activity in stressed mice. Combination of PDTC and diazepam also served to produce a higher significant antianxiety-like activity in stressed mice than that produced by PDTC alone. Diazepam could not produce any change in plasma nitrite levels in both unstressed and stressed mice. Both SB-203580 (2 mg/kg, i.p.) and PDTC (100 mg/kg, i.p.) significantly decreased plasma nitrite levels in stressed mice. The observations indicate that the diminished anti-anxiety effect of diazepam in stressed mice may involve strong nitriergic influence and may further be p38MAPK- and NF-κB-dependent.

Nitric Oxide Synthase Inhibitors as Antidepressants

Affective and anxiety disorders are widely distributed disorders with severe social and economic effects. Evidence is emphatic that effective treatment helps to restore function and quality of life. Due to the action of most modern antidepressant drugs, serotonergic mechanisms have traditionally been suggested to play major roles in the pathophysiology of mood and stress-related disorders. However, a few clinical and several pre-clinical studies, strongly suggest involvement of the nitric oxide (NO) signaling pathway in these disorders. Moreover, several of the conventional neurotransmitters, including serotonin, glutamate and GABA, are intimately regulated by NO, and distinct classes of antidepressants have been found to modulate the hippocampal NO level in vivo. The NO system is therefore a potential target for antidepressant and anxiolytic drug action in acute therapy as well as in prophylaxis. This paper reviews the effect of drugs modulating NO synthesis in anxiety and depression.