Effects of serotonin depletion on behavior and neuronal oxidative stress status in rat: relevance for anxiety and affective disorders

Chronic mild stress induces differential depression-like symptoms and c-Fos and 5HT1A protein levels in high-anxiety female Long Evans rats

Depression and anxiety disorders overlap in clinical populations, suggesting common mechanisms that may be further investigated in reliable animal models. We used filial 8 female Long-Evans rats bred for high (HAn; n = 19) and low anxiety (LAn)-like behavior (n = 21) to assess forced swim test mobility strategies and chronic mild stress (CMS)-induced depression-like symptoms. We measured (1) weight, (2) fur piloerection, (3) sweet food consumption, (4) grooming behavior, and (5) circulating estradiol (E2). One month after CMS terminated and following a terminal forced swim test, brains were processed for immunohistochemistry targeting c-Fos and serotonin 1 A receptor (5-HT1AR) protein in the paraventricular nucleus (PVN) of the hypothalamus. HAn female rats showed increased anxiety-like behavior (i.e., lower open to closed arm ratios, increased closed arm entries), more swimming (i.e., mobility), and less floating (i.e., immobility) behavior in the forced swim test. Overall, HAn females weighed less than their LAn counterparts. After chronic mild stress, HAn lines displayed even greater mobility and consumed fewer Froot Loops™. Fur and grooming analyses indicated no significant differences in mean counts across experimental groups. One month after CMS, cycling E2 concentrations (pg/ml) did not differ between HAn and LAn animals. Elevated c-Fos and 5-HT1AR expression were observed in the PVN, where HAn CMS rats expressed the most c-Fos and 5-HT1AR immunoreactivity. In summary, outbred HAn rats show robust anxiety-like behavior, exhibit more mobility in the forced swim test, and are more sensitive to chronic mild stress-induced grooming and decline in palatable food ingestion.

Neurodegenerative Diseases: Implications of Environmental and Climatic Influences on Neurotransmitters and Neuronal Hormones Activities

Neurodegenerative and neuronal-related diseases are major public health concerns. Human vulnerability to neurodegenerative diseases (NDDs) increases with age. Neuronal hormones and neurotransmitters are major determinant factors regulating brain structure and functions. The implications of environmental and climatic changes emerged recently as influence factors on numerous diseases. However, the complex interaction of neurotransmitters and neuronal hormones and their depletion under environmental and climatic influences on NDDs are not well established in the literature. In this review, we aim to explore the connection between the environmental and climatic factors to NDDs and to highlight the available and potential therapeutic interventions that could use to improve the quality of life and reduce susceptibility to NDDs.

Serotonin depletion during the postnatal developmental period causes behavioral and cognitive alterations and decreases BDNF level in the brain of rats

A survey of the literature indicates that the developmental disruptions in serotonin (5-HT) levels can influence the brain development and the function. To the best of our knowledge, so far, there are a few studies about the effects of developmental period 5-HT depletion on cognition and behavior of adult male and female rats. Therefore, in the present study, we examined the effects of postnatal days (PND 10-20) administration of para-chlorophenylalanine (PCPA, 100 mg/kg, s.c) a 5-HT synthesis inhibitor, on anxiety-related behaviors, pain sensitivity, short-term recognition memory, and hippocampal and prefrontal cortex (PFC) brain-derived neurotrophic factor (BDNF) mRNA expression in adult male and female rats. Novel object recognition memory (NORM) and behavioral parameters (anxiety-like behaviors and pain sensitivity) were evaluated in early adulthood and after that, the hippocampi and PFC of the rat's brain were removed for the determination of BDNF mRNA expression. Our results indicated that the postnatal period administration of PCPA impaired short-term NORM. The postnatal developmental period treatment with PCPA also increased anxiety-like behaviors in the open field and elevated plus maze (EPM) tests. Postnatal PCPA treatment increased pain sensitivity in the hot plate test in both male and female rats, especially in female animals. In addition, postnatal days serotonin depletion decreased BDNF level in the hippocampus and PFC of both male and female rats. These findings demonstrate that serotonin plays the main role in neurodevelopment, cognitive functions, and behavior. Therefore, serotonergic system dysregulation during the developmental periods may have more adverse influences on the brain development of rats.

Beneficial effects of crataegus oxyacantha extract on neurobehavioral deficits and brain tissue damages induced by an insecticide mixture of deltamethrin and chlorpyrifos in adult wistar rats

Pesticides, such as organophosphorus and pyrethroids, are extensively used in the agrofields which can significantly increase crop productivity. Humans are exposed to pesticides via dermal contact, inhalation and ingestion due to occupational exposure. The objective of the present study was to evaluate the protective role of the aqueous extract of Crataegus oxyacantha during acute exposure of rats to the combination of deltamethrin (DM) and chlorpyrifos (CPF) in rats (DCF). The combination of vitamins C and E (Vit CE) was used as a standard antioxidant. The Crataegus oxyacantha extract revealed the presence of a high level of phenolic compounds identified by HPLC analysis. Male wistar rats were divided into six groups: (I) corn oil, (II) AECO (1 ml/100 g), (III) DCF (DM 5 mg/kg, CPF 1 mg/kg), (IV) AECO + DCF, (V) Vit CE (Vit C 100 mg/kg, Vit E 100 mg/kg), and (VI) Vit CE + DCF. AECO and Vit CE were administered 10 days before the administration of DCF. The findings revealed that the administration of DM and CPF mixture induced a significant decrease in serum AChE and DNA damage, as indicated by brain DNA fragmentation. In addition, behavioral tests by open field and elevated plus maze showed impaired recognition memory. The results showed that AECO or Vit CE alleviated significantly neurobehavioral alterations, reduced lipid peroxidation in brain, and restored the antioxidant parameters (SOD, CAT, GPx and GSH) to normal levels. Furthermore, brain DNA fragmentation and histopathology in DCF treated rats were improved by AECO administration. All results revealed that C. oxyacantha extract, rich in polyphenolic compounds, had potential antioxidant effects on the combination of DM and CPF-induced oxidative brain damage.

Serotonin transporter gene linked polymorphism (5-HTTLPR) determines progredience of alcohol dependence in Belarusian young males

PURPOSE

Allelic duality and functional impact of degenerate repeat at 5'- flanking promoter region in SLC6A4 gene of the serotonin transporter (5-HTTLPR), have been in the focus of investigations over the years. Various outcomes regarding an association of its polymorphism with risks of alcohol dependence syndrome (ADS) were presented. Such studies have not been conducted in the Eastern European population e.g. Belarus. We therefore checked: the association of 5-HTTLPR polymorphism with ADS, and functional impact of the polymorphism on progredience of ADS in Belarusian population.

MATERIAL AND METHODS

The study involved 499 Belarusian males: 377 subjects with ADS (AG), and a control group (CG) with 122 subjects without alcohol-related problems. The ADS group was further divided into two groups of individuals with rapid (AG (R)) and delayed (AG (D)) progression of ADS. Clinical diagnosis was carried-out using ICD-10 criteria, Belarusian Addiction Severity Index, "B-ASI" and Alcohol-Use-Disorders-Identification-Test (AUDIT). PCR-RFLP analysis was performed.

RESULTS

There were no significant differences in the distribution of frequencies of either the 5-HTTLPR genotype or the short and long allele among AG and CG. However, the ADS 5-HTTLPR genotype and allele distribution frequencies differ significantly by the variation in progression of ADS.

CONCLUSIONS

There is no significant association between polymorphism of serotonin transporter gene and risk of ADS. However, the polymorphism significantly determines progredience of ASD in subjects with pathological patterns of alcohol consumption. Findings from this study carry preliminary significance as a facility to effective alcohol addiction treatment, rehabilitation and preventive services in the Eastern Europe.

On the Neurobiological Role of Oxidative Stress in Alcohol-Induced Impulsive, Aggressive and Suicidal Behavior

Objectives: Alcohol abuse is known to result in behavioral impairments (such as increased impulsivity, aggressive, and suicidal behavior), but the neurobiological basis for these behavioral impairments remains unknown. The objective of this review is to propose a neurobiological basis for alcohol-induced aggression, impulsivity, and suicidal behavior. Methods: Search was done by accessing PubMed/Medline, EBSCO, and PsycINFO databases. The search string used was "(Alcohol OR Alcoholism* OR Alcohol Abuse) AND (Behavior* OR Behavioral Impairment or Disorder) AND (Oxidative Stress OR Reactive Oxygen Species)." The electronic databases were searched for titles or abstracts containing these terms in all published articles between January 1, 1960, and May 31, 2019. The search was limited to studies published in English and other languages involving both animal and human subjects. Articles selected included randomized clinical trials (RCTs), observational studies, meta-analyses, and both systemic and narrative reviews, providing both quantitative and qualitative information with a measure of alcohol abuse or alcoholism as an outcome. Exclusion criteria were unpublished data of any form, including conference proceedings and dissertation. New key terms were identified (new term included: "Antioxidants, Neurotransmitters, Dopamine, Serotonin, GABA, Glutamate. Aggression, Impulsivity, Suicidal Behavior, hippocampus, prefrontal cortex, limbic system, psychiatric disorders, PTSD, Anxiety, Depression. These new terms were searched with Alcohol or Alcoholism or Alcohol Abuse and Oxidative Stress separately resulting in the identification of over 3000 articles. 196 were included in this article. Results: Multiple lines of evidence indicate that oxidative stress (OS) plays a critical underlying role in alcohol toxicity and behavioral impairments. Conclusions/Importance: People diagnosed with PTSD, anxiety disorder, depression, and those with a personality high in psychoticism as measured by the P Scale of the Eysenck Personality Questionnaire, with comorbid alcohol abuse or alcohol use disorder (AUD), may display increased impulsivity, aggression, and suicidal behavior because of the potentiating effect of alcohol-induced OS on their elevated brain oxidative status. Antioxidant therapy should be an integral part of acute alcohol intoxication and AUD treatment. Further research is necessary to fully understand the relationship between OS and alcohol-induced behavioral impairments.

Protective effects of Curcuma longa against neurobehavioral and neurochemical damage caused by cerium chloride in mice

Cerium chloride (CeCl₃) is considered an environmental pollutant and a potent neurotoxic agent. Medicinal plants have many bioactive compounds that provide protection against damage caused by such pollutants. Curcuma longa is a bioactive compound-rich plant with very important antioxidant properties. To study the preventive and healing effects of Curcuma longa on cerium-damaged mouse brains, we intraperitoneally injected cerium chloride (CeCl₃, 20 mg/kg BW) along with Curcuma longa extract, administrated by gavage (100 mg/kg BW), into mice for 60 days. We then examined mouse behavior, brain tissue damage, and brain oxidative stress parameters. Our results revealed a significant modification in the behavior of the CeCl₃-treated mice. In addition, CeCl₃ induced a significant increment in lipid peroxidation, carbonyl protein (PCO), and advanced oxidation protein product levels, as well as a significant reduction in superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities. Acetylcholinesterase (AChE) activity remarkably increased in the brain of CeCl₃-treated mice. Histopathological observations confirmed these results. Curcuma longa attenuated CeCl₃-induced oxidative stress and increased the activities of antioxidant enzymes. It also decreased AChE activity in the CeCl₃-damaged mouse brain that was confirmed by histopathology. In conclusion, this study suggests that Curcuma longa has a neuroprotective effect against CeCl₃-induced damage in the brain.

The role of oxidative stress in anxiety disorder: cause or consequence?

Anxiety disorders are the most common mental illness in the USA affecting 18% of the population. The cause(s) of anxiety disorders is/are not completely clear, and research in the neurobiology of anxiety at the molecular level is still rather limited. Although mounting clinical and preclinical evidence now indicates that oxidative stress may be a major component of anxiety pathology, whether oxidative stress is the cause or consequence remains elusive. Studies conducted over the past few years suggest that anxiety disorders may be characterised by lowered antioxidant defences and increased oxidative damage to proteins, lipids, and nucleic acids. In particular, oxidative modifications to proteins have actually been proposed as a potential factor in the onset and progression of several psychiatric disorders, including anxiety and depressive disorders. Oxidised proteins are normally degraded by the proteasome proteolytic complex in the cell cytoplasm, nucleus, and endoplasmic reticulum. The Lon protease performs a similar protective function inside mitochondria. Impairment of the proteasome and/or the Lon protease results in the accumulation of toxic oxidised proteins in the brain, which can cause severe neuronal trauma. Recent evidence points to possible proteolytic dysfunction and accumulation of damaged, oxidised proteins as factors that may determine the appearance and severity of psychotic symptoms in mood disorders. Thus, critical interactions between oxidative stress, proteasome, and the Lon protease may provide keys to the molecular mechanisms involved in emotional regulation, and may also be of great help in designing and screening novel anxiolytics and antidepressants.

Phytochemistry, bioactivity: suggestion of Ceratonia siliqua L. as neurodegenerative disease therapy

Carob tree (Ceratonia siliqua L.) is one of the most widespread medicinal plants in the Mediterranean area. Traditionally, it was cultivated for its ethnopharmacological benefits and, more especially, for the seeds, which served as unit of measurement of jewelers "carat." Hence, in the last half-century, numerous studies reported a wide range of phytoconstituents contained in all parts of Ceratonia siliqua such as phenolic compounds, flavonoids, tannins, anthocyanins, alkaloids, glycosides, proteins and minerals. This review article unveils the phytochemical constituents, bioactivity and pharmacological studies of Ceratonia siliqua. Recent studies have shown that the extracts of this plant exhibit an antioxidant, antidiarrheal, antibacterial, antifungal, anti-inflammatory, antidiabetic activities and also hepatoprotective and antiproliferative effects. In this review, we provide a summary of the most interesting data related to bioactivity and therapeutic potential of Ceratonia siliqua in a way to suggest possible future studies that may use Ceratonia siliqua as an undeniable natural alternative for neurodegenerative diseases treatment.

Describing some behavioural animal models of anxiety and their mechanistics with special reference to oxidative stress and oxytocin relevance

It is now generally accepted that animal studies are playing an important role in the understanding of anxiety disorders, since they contribute to the current knowledge regarding the mechanisms and possible therapeutic approaches in anxiety. In the present review we will detail some essential aspects of behavioral animal models of anxiety related to social defeat paradigm, elevated plus maze, elevated zero or T maze, light/dark box, social interaction test or tests based on predator models, considering the latest theories and methodological approaches in this area of research, as well as our previous studies focusing on anxiety manifestations in a variety of species including rats, zebrafish, dogs and pigs. Moreover, in this context, we will focus on the recent theories concerning oxidative stress, as well as importance of oxytocin administration (especially the intranasal route). This could be important considering that these two factors are currently being investigated as possible mechanisms (oxidative stress status) and related therapeutic target (both intranasal oxytocin and antioxidants) in the pathology of the anxiety disorders.

Angiotensin AT1 receptors modulate the anxiogenic effects of angiotensin (5-8) injected into the rat ventrolateral periaqueductal gray

Losartan and PD 123,319 are non-peptide angiotensin (Ang) receptor antagonists for the AT1 and AT2 subtypes of Ang II receptors, respectively. The tetrapeptide Ang (5-8) is the smallest Ang-peptide that elicits anxiogenic effects on unconditioned and conditioned experimental models upon injection into the ventrolateral column of the periaqueductal gray (vlPAG), and Ang (5-8) can be synthesized (from Ang II or Ang III) and inactivated in this mesencephalic structure. The vlPAG is also known to play a central role in mechanisms of fear and anxiety. We therefore utilized male Wistar rats to examine the effects of losartan and PD 123,319 injections, selective antagonists of the AT1 and AT2 receptors, respectively, into the vlPAG in the elevated plus-maze, a classic rat model of anxiety, and against the anxiogenic effect of Ang (5-8) (0.4 nmol/0.25μL) upon injection into the same region. The anxiolytic profile was dependent on the dose of intra-vlPAG losartan, whereas no effects on experimental anxiety were observed in the plus-maze following PD 123,319 injection. The anxiogenic effect of Ang (5-8) injection into the vlPAG remained unchanged in the PD 123,319-pretreated rats, but the effect did not occur in losartan-pretreated rats. The results led us to suggest that the anxiogenic effect of Ang (5-8) injection into the vlPAG may depend on the local activation of AT1, but not AT2 receptors. Activation of AT1 receptors in structures nearby vlPAG may be tonically involved in fear and experimental anxiety.

Restoring Spinal Noradrenergic Inhibitory Tone Attenuates Pain Hypersensitivity in a Rat Model of Parkinson's Disease

In the present study, we investigated whether restoring descending noradrenergic inhibitory tone can attenuate pain in a PD rat model, which was established by stereotaxic infusion of 6-hydroxydopamine (6-OHDA) into the bilateral striatum (CPu). PD rats developed thermal and mechanical hypersensitivity at the 4th week after surgery. HPLC analysis showed that NE content, but not dopamine or 5-HT, significantly decreased in lumbar spinal cord in PD rats. Additional noradrenergic depletion by injection of N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) aggravated pain hypersensitivity in PD rats. At the 5th week after injection of 6-OHDA, systemic treatment with pharmacological norepinephrine (NE) precursor droxidopa (L-DOPS) or α2 adrenoceptor agonist clonidine significantly attenuated thermal and mechanical pain hypersensitivity in PD rats. Furthermore, application of norepinephrine (NE) and 5-hydroxytryptamine (5-HT) reuptake inhibitors duloxetine, but not 5-HT selective reuptake inhibitors sertraline, significantly inhibited thermal and mechanical pain hypersensitivity in PD rats. Systemic administration of Madopar (L-DOPA) or the D2/D3 agonist pramipexole slightly inhibited the thermal, but not mechanical, hypersensitivity in PD rats. Thus, our study revealed that impairment of descending noradrenergic system may play a key role in PD-associated pain and restoring spinal noradrenergic inhibitory tone may serve as a novel strategy to manage PD-associated pain.

Oxidative Stress Implications in the Affective Disorders: Main Biomarkers, Animal Models Relevance, Genetic Perspectives, and Antioxidant Approaches

The correlation between the affective disorders and the almost ubiquitous pathological oxidative stress can be described in a multifactorial way, as an important mechanism of central nervous system impairment. Whether the obvious changes which occur in oxidative balance of the affective disorders are a part of the constitutive mechanism or a collateral effect yet remains as an interesting question. However it is now clear that oxidative stress is a component of these disorders, being characterized by different aspects in a disease-dependent manner. Still, there are a lot of controversies regarding the relevance of the oxidative stress status in most of the affective disorders and despite the fact that most of the studies are showing that the affective disorders development can be correlated to increased oxidative levels, there are various studies stating that oxidative stress is not linked with the mood changing tendencies. Thus, in this minireview we decided to describe the way in which oxidative stress is involved in the affective disorders development, by focusing on the main oxidative stress markers that could be used mechanistically and therapeutically in these deficiencies, the genetic perspectives, some antioxidant approaches, and the relevance of some animal models studies in this context.

Evaluation of oxidative and antioxidative parameters in generalized anxiety disorder

Generalized anxiety disorder (GAD) is a prevalent psychiatric disorder. The exact causes of GAD still unknown, in addition to neurochemical and neuroanatomic disorders, genetic and environmental factors are discussed in etiology. In our study we aimed to evaluate the oxidative metabolism's status and investigate the role of oxidative metabolites in GAD. Blood samples were taken from enrolled subjects in appropriate way and total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI) were studied in Harran University Biochemistry Labs. Results were compared between groups. The patients' TOS and OSI levels were significantly higher than control group. The patients' TAS levels were significantly lower than controls'. According to our findings, oxidative stress mechanism might have a role in GAD pathophysiology. In the future, total antioxidants may be used as a biologic marker in GAD etiology but more research is needed.

Individual differences in cocaine addiction: maladaptive behavioural traits

Cocaine use leads to addiction in only a subset of individuals. Understanding the mechanisms underlying these individual differences in the transition from cocaine use to cocaine abuse is important to develop treatment strategies. There is agreement that specific behavioural traits increase the risk for addiction. As such, both high impulsivity and high anxiety have been reported to predict (compulsive) cocaine self-administration behaviour. Here, we set out a new view explaining how these two behavioural traits may affect addictive behaviour. According to psychological and psychiatric evolutionary views, organisms flourish well when they fit (match) their environment by trait and genotype. However, under non-fit conditions, the need to compensate the failure to deal with this environment increases, and, as a consequence, the functional use of rewarding drugs like cocaine may also increase. It suggests that neither impulsivity nor anxiety are bad per se, but that the increased risk to develop cocaine addiction is dependent on whether behavioural traits are adaptive or maladaptive in the environment to which the animals are exposed. This 'behavioural (mal)adaptation view' on individual differences in vulnerability to cocaine addiction may help to improve therapies for addiction.

Oxidative imbalance and anxiety disorders

The oxidative imbalance appears to have an important role in anxiety development. Studies in both humans and animals have shown a strong correlation between anxiety and oxidative stress. In humans, for example, the increased malondialdehyde levels and discrepancies in antioxidant enzymes in erythrocytes have been observed. In animals, several studies also show that anxiety-like behavior is related to the oxidative imbalance. Moreover, anxiety-like behavior can be caused by pharmacological-induced oxidative stress. Studies using knockout or overexpression of antioxidant enzymes have shown a relationship between anxiety-like behavior and oxidative stress. Related factors of oxidative stress that could influence anxious behavior are revised, including impaired function of different mitochondrial proteins, inflammatory cytokines, and neurotrophic factors. It has been suggested that a therapy specifically focus in reducing reactive species production may have a beneficial effect in reducing anxiety. However, the neurobiological pathways underlying the effect of oxidative stress on anxiety symptoms are not fully comprehended. The challenge now is to identify the oxidative stress mechanisms likely to be involved in the induction of anxiety symptoms. Understanding these pathways could help to clarify the neurobiology of the anxiety disorder and provide tools for new discovery in therapies and preventive strategies.

Angiotensin-(1-7) central administration induces anxiolytic-like effects in elevated plus maze and decreased oxidative stress in the amygdala

There is increasing evidence that besides the well-known angiotensin (Ang) II, other renin-angiotensin system (RAS) peptides, including Ang-(1-7), could have important effects at the central level. However, very few things are known about the central actions of Ang-(1-7), while the effects of its administration alone on anxiety have not been tested to date, to the best of our knowledge. In this way, we were interested in studying the effects of Ang-(1-7) intracerebroventricular administration on anxiety levels, as studied through some main behavioral parameters in the elevated plus maze, as well as the importance of Ang-(1-7) in the oxidative stress status from the amygdala, which is one of the key brain regions involved in mediating anxiety. We report here a possible anxiolytic-like effect of Ang-(1-7) administration, as demonstrated by the increased percentage of time spent and frequency of entries in the open arms of the elevated plus maze, as well as increased head-dipping behavior in the open arms and decreased stretching in closed arms. Also some antioxidant effects of Ang-(1-7) are suggested since a significant increase of GPX specific activity and a decrease of the main peroxidation marker MDA were observed in the amygdala. Moreover, we found a significant correlation between most of the behavioral parameters in the elevated plus maze and the levels of the oxidative stress markers. However, further studies are necessary in order to elucidate the effects of Ang-(1-7) administration on anxiety and oxidative stress status and also on the possible correlation that might exists between these aspects.

The Effects of Central Angiotensin II and Its Specific Blockers on Nociception. Possible Interactions with Oxidative Stress Status / Efekti Centralnog Angiotenzina II I Njegovih Specifičnih Blokatora Na Nocicepciju. Moguće Interakcije Sa Statusom Oksidativnog Stresa

It has already been demonstrated that a complete brain renin-angiotensin system (RAS) exists distinctly separate from the peripheral system and is implicated in complex functions such as memory, emotional responses and pain. Regarding the implications of angiotensin II (the main bioactive peptide of RAS) in pain, although there are many studies in this area of research, most of the results are controversial. Also, it seems that oxidative stress follows angiotensin II infusion, but the role of AT1 vs. AT2 receptors is not well established. In this context, we were interested in studying the effects of central RAS on nociception, through the intracerebroventricular administration of losartan and PD-123177 (antagonists for the AT1/AT2 receptors), as well as an ACE inhibitor (captopril) and also angiotensin II in rats, which were subsequently tested using the hot-plate task, a well known behavioral test for pain perception. We present here the analgesic effect of angiotensin II administration, as shown by in creased latency-time in the hot-plate, as well as a nociceptive effect of angiotensin II blockers like AT1 and AT2 specific antagonists (losartan and PD-123177) and an ACE inhibitor (captopril), as their administration resulted in decreased latency-time. Moreover, we demonstrated a significant correlation between the results of the nociceptive behavioral task and the levels of some main oxidative stress markers. This provides additional evidence for an analgesic effect of Ang II administration, as well as for a nociceptive effect of Ang II blockers. Moreover, a significant correlation between the nociception and angiotensin II-induced oxidative stress is presented.

The interdependence of the reactive species of oxygen, nitrogen, and carbon

This mini-review tries to summarize the main interdependences between the free radicals of oxygen, nitrogen, and carbon. Also, the main metabolic pathways for these radical species are described, as well as how these affect their interaction and functional implications. Emphasis is made on the metabolic disturbances induced by stressing aggressions that produce radical species. In this way, cellular oxidative imbalances created by the superiority of reactive oxygen species over the antioxidant systems produce both activation of nitroxide synthases and the oxidation of terminal nitrogen from L-arginine, as well as the metabolization of heme until carbon monoxide by nitric oxide-activated hemoxygenase. Also, multiple cellular protein and nucleoprotein alterations determined by these three kinds of radical species are completed by the involvement of hydrogen sulfide, which results from the degradation of L-cysteine by cistationine-γ-lyase. In this way, sufficient experimental data tend to demonstrate the involvement of hydrogen sulfide and other thiol derivatives in the interrelations between oxygen, nitrogen, and carbon, which results in a true radical cascade. Thus, oxidative stress, together with nitrosative and carbonilic stress, may constitute a central point where other factors of vulnerability meet, and their interactions could have an important impact in many modern diseases. Considering that the actions of reactive species can be most of the time corrected, future studies need to establish the therapeutical importance of various agents which modulate oxidative, nitrosative, or carbonilic stress.

Anxiety-like behavior and cognitive flexibility in adult rats perinatally exposed to increased serotonin concentrations

Serotonin (5-hydroxytryptamine, 5HT) is a biologically active amine that regulates the development of 5HT neurons and target tissues during neurogenesis, while later it assumes the function of a neurotransmitter. Serotonin mediates many essential behaviors common to all mammals, and is held responsible for anxiety-like behavior and cognitive rigidity. Proper serotonin levels, controlled through 5HT synthesis and metabolism, are crucial for normal brain development. In this study we investigated anxiety-like behavior and cognitive flexibility in adult animals after exposing their developing brains to increased 5HT concentrations. Wistar rats were treated subcutaneously from gestational day 12 to post-natal day 21 with the immediate 5HT precursor 5-hydroxytryptophan (5HTP, 25mg/kg), a non-selective MAO inhibitor tranylcypromine (TCP, 2mg/kg), or saline. After reaching adulthood, animals were tested for anxiety-like behavior (exploratory behavior, thigmotactic behavior, social contact, and reaction to stressful stimulus) and cognitive flexibility (ability for reversal learning). Results of the behavioral studies corresponded with our previous neurochemical findings. Treatment with 5HTP, which has induced mild reduction in cortical 5HT concentrations, caused reduction in only one aspect of anxiety-like behavior (increased exploratory activity). Treatment with TCP, which lead to drastic reduction in 5HT concentration/function, resulted in a highly anxiolytic phenotype (reduced thigmotaxis, reaction to stress, and social anxiety) with improved cognitive flexibility. Although further neurochemical, anatomical and gene-expression studies are needed to elucidate the mechanisms underlying the observed behavior, we hope that our results will contribute to the understanding of the role of serotonin in anxiety-like behavior and cognitive rigidity.

Serotonergic and noradrenergic pathways are required for the anxiolytic-like and antidepressant-like behavioral effects of repeated vagal nerve stimulation in rats

BACKGROUND

Vagal nerve stimulation (VNS) is used for treatment-refractory depression, but there are few preclinical studies of its effects when administered repeatedly over time using clinically relevant stimulation parameters in nonanesthetized animals.

METHODS

The novelty-suppressed feeding test (NSFT) and forced swim test (FST) were used to evaluate the anxiolytic- and antidepressant-like potential of VNS in rats, respectively. The behavioral effects of VNS were compared with those of desipramine (DMI; 10 mg/kg/day) and sertraline (7.5 mg/kg/day) administered via osmotic minipump. Such experiments were carried out in intact rats as well as those that had selective destruction of either serotonin or noradrenergic neurons in brain caused by the neurotoxins, 5,7-dihyroxytryptamine (5,7-DHT), or 6-hydroxydopamine (6-OHDA).

RESULTS

Repeated administration of VNS, DMI, and sertraline decreased latency to feed in the NSFT. In the FST, repeated VNS, DMI, and sertraline caused decreased immobility; the VNS-induced decrease in immobility resulted from increases in both swimming and climbing behaviors. Effects of VNS and sertraline, but not DMI, in both the NSFT and the FST were abolished in rats treated with 5,7-DHT. Effects of DMI in both behavioral tests, but not those of sertraline, were abolished in 6-OHDA treated rats. VNS effects on immobility and climbing in the FST were not blocked in the 6-OHDA-treated rats. There was no significant difference in locomotor activity caused by any of the treatments or by the lesions.

CONCLUSIONS

Serotonergic nerves are required for repeated VNS-induced anxiolytic- and antidepressant-like effects. Noradrenergic nerves can also be activated by VNS to cause its anxiolytic-like effect.

The effects of pergolide on memory and oxidative stress in a rat model of Parkinson's disease

One of the most widely used animal models of Parkinson's disease (PD) involves injecting 6-hydroxydopamine (6-OHDA) directly into the substantia nigra (SN). Some recent reports speculated that dopaminergic drugs may exert brain antioxidant activity, which could explain some of their protective actions. In this way, the aim of the present study was to examine the effects of low-dose pergolide on memory deficits and brain oxidative stress in a 6-OHDA-induced rat model of PD. Right-unilateral lesions of the SN were produced with 6-OHDA. Two weeks after neurosurgery, pergolide (0.3 mg/kg/day) was injected intraperitoneally in the 6-OHDA + pergolide and sham-operated + pergolide groups, while sham-operated and 6-OHDA alone groups received saline. Radial-8-arm maze and Y-maze were used for memory assessment. We also determined some enzymatic antioxidant defenses like superoxide dismutase or glutathione peroxidase and a lipid peroxidation marker [malondialdehyde (MDA)], from the temporal lobe. A reduced number of working/reference memory errors was observed in 6-OHDA + pergolide group, compared to sham-operated rats. Additionally, post hoc analysis showed significant differences between 6-OHDA and 6-OHDA + pergolide groups in both Y-maze and radial-arm-maze tasks. We also noted a significant decrease of MDA level in the 6-OHDA + pergolide group, compared to sham-operated rats. Significant correlations were also found between behavioral parameters and MDA levels. Our data suggest that pergolide facilitates spatial memory and improves brain oxidative balance, after a 6-OHDA-induced model of PD. This could be useful for further investigations and clinical applications of pergolide.

Antioxidants prevent memory deficits provoked by chronic variable stress in rats

Learning and memory deficits occur in depression and other stress related disorders. Although the pathogenesis of cognitive impairment after stress has not been fully elucidated, factors such as oxidative stress and neurotrophins are thought to play possible roles. Here we investigated the effect of treatment with vitamin E (40 mg/kg) and vitamin C (100 mg/kg) on the effects elicited by chronic variable stress on rat performance in Morris water maze. Brain-derived neurotrophic factor (BDNF) immunocontent was also evaluated in hippocampus of rats. Sixty-day old Wistar rats were submitted to different stressors for 40 days (stressed group). Half of stressed group received administration of vitamins once a day, during the period of stress. Chronically stressed rats presented a marked decrease in reference memory in the water maze task as well as a reduced efficiency to find the platform in the working memory task. Rats treated with vitamins E and C had part of the above effects prevented, suggesting the participation of oxidative stress in such effects. The BDNF levels were not altered in hippocampus of stressed group when compared to controls. Our findings lend support to a novel therapeutic strategy, associated with these vitamins, to the cognitive dysfunction observed in depression and other stress related diseases.

Sodium oxybate for the treatment of fibromyalgia

INTRODUCTION

Gamma-hydroxybutyrate (GHB) is a short-chain fatty acid that is synthesized within the CNS, mostly from its parent compound gamma amino butyric acid (GABA). GHB acts as a neuromodulator/neurotransmitter to affect neuronal activity of other neurotransmitters and so, stimulate the release of growth hormone. Its sodium salt (sodium oxybate: SXB) was approved by the Food and Drug Administration (FDA) for the treatment of narcolepsy. SXB has shown to improve disrupted sleep and increase NR3 (slow-wave restorative) sleep in patients with narcolepsy. It is rapidly absorbed and has a plasma half-life of 30 - 60 min, necessitating twice-nightly dosing. Most of the observed effects of SXB result from binding to GABA-B receptors.

AREAS COVERED

Several randomized, controlled trials demonstrated significantly improved fibromyalgia (FM) symptoms with SXB. As seen in narcolepsy trials, SXB improved sleep of FM patients, increased slow-wave sleep duration as well as delta power, and reduced frequent night-time awakenings. Furthermore, FM pain and fatigue was consistently reduced with nightly SXB over time. Commonly reported adverse events included headache, nausea, dizziness and somnolence. Despite its proven efficacy, SXB did not receive FDA approval for the management of FM in 2010, mostly because of concerns about abuse.

EXPERT OPINION

Insomnia, fatigue and pain are important clinical FM symptoms that showed moderate improvements with SXB in several large, well-designed clinical trials. Because of the limited efficacy of currently available FM drugs additional treatment options are needed. In particular, drugs like SXB - which belong to a different drug class than other Food and Drug Administration (FDA)-approved FM medications such as pregabalin, duloxetine and milnacipran - would provide a much-needed addition to presently available treatment options. However, the FDA has set the bar high for future SXB re-submissions, with requirements of superior efficacy and improved risk mitigation strategies. At this time, no future FDA submission of SXB for the fibromyalgia indication is planned.

Effects of angiotensin II receptor antagonists on anxiety and some oxidative stress markers in rat

In addition to its known classical roles, the renin angiotensin system (RAS) has more subtle functions which include the regulation of emotional responses. Previous studies regarding the anxiety related behavior of RAS have showed controversial results. There is also evidence that oxidative stress accompanies angiotensin II infusion, but the role of AT1/AT2 specific receptors is not clear. The aim of this study was to evaluate the effects of central angiotensin II receptor blockers on anxiety state and oxidative stress. Behavioral testing included elevated plus maze, while oxidative stress status was measured though the extent of a lipid peroxidation product (malondialdehyde-MDA) and the specific activity of some defense antioxidant enzymes (superoxide dismutase-SOD and glutathione peroxidase-GPx). The rats treated with angiotensin II spent significantly less time in the open-arms of elevated-plus-maze, while the administration of losartan resulted in a significant increase of this time. We observed a significant increase of MDA concentration in the angiotensin II group and a decrease of MDA levels in both losartan and PD-123177 groups. In addition, a significant correlation was seen between the time spent in the open arms and oxidative stress markers. These findings could lead to important therapeutic aspects regarding the use of angiotensin II receptor blockers in anxiety-related disorders.