The use of the elevated plus maze as an assay of anxiety-related behavior in rodents

Toxic effects of the ingestion of water-soluble elements found in soil under the atmospheric influence of an industrial complex

In this study, we investigated the toxic effects of water-soluble elements from a contaminated soil via gavage in a single dose, simulating a geophagy event. The contaminated soil was collected in a field located in an industrial complex, and the control soil was collected in a reference area. Metabolic and behavioral parameters in Wistar male rats were measured after 24 and 96 h of gavage. After 96 h, the major organs were weighed, blood was collected to check hematological parameters, the bone marrow was taken for the micronucleus test, and the liver was used for evaluating the total antioxidant capacity, lipoperoxidation and protein carbonylation. Animals exposed to contaminated soil presented a few significant alterations by comparison with control animals: TBARS and protein carbonyl levels increased, the relative weight of the kidneys increased, metabolic parameters (body weight gain, food intake, water consumption, urine and feces production) depressed and there was behavioral alteration. These findings suggest that soils impacted by atmospheric contaminants can affect the organism physiological status jeopardizing the health of populations living in industrial areas. Finally, this study reassures that ingestion of potentially contaminated soils, even for short periods of time, can cause health risks.

Environmental enrichment effects on the neurobehavioral profile of selective outbred trait anxiety rats

Environmental enrichment attenuates the response to psychostimulants and has been shown to reduce both anxiety and stress-related behaviors. Since stress is a major vulnerability factor for addiction, we investigated whether enrichment could reverse stress profiles in high anxious rats as well as reduce their amphetamine sensitivity. Using selectively-bred high and low anxiety males (filial 3) from enriched, social or isolated environments, we tested elevated plus maze exploration, novelty place preference and amphetamine (AMPH; 0.5mg/kg, IP)-induced hyperactivity. We measured plasma corticosterone (CORT) response after forced novel object exposure, phosphorylation of the tropomyosin-related kinase B receptor (pTrkB) in the hippocampus and striatum, and dopamine (D2) receptor mRNA levels in the striatum and nucleus accumbens. Results indicate that high anxiety animals reared in social or enriched environments spent more time on open arms of the EPM while low anxiety animals raised in enriched environments spent more time on open arms when compared to either isolated or social groups. There were no group differences or interactions found for novelty place preference. Enriched environments decreased the response to AMPH and stress-induced CORT regardless of trait but selectively decreased pTrkB and increased D2 mRNA levels in high anxiety animals. The results suggest that selectively-bred trait anxiety rats show state anxiety that is influenced by rearing environments, and D2 protein levels and BDNF/TrkB signaling may differentially contribute to integrating these effects.

Behavioral and neuronal biochemical possible effects in experimental induced chronic mild stress in male albino rats under the effect of oral barley administration in comparison to venlafaxine

Venlafaxine is an antidepressant of choice, whose effectiveness could be modified by a commonly used medicinal plant and nutrient. The current study had evaluated the barley extract (1 g/kg) when compared to or combined to venlafaxine (32 mg/kg) in a rat stress model. The present study was conducted on 40 male Wister albino rats; divided to five groups. Four groups were subjected to social chronic mild stress. Drugs or saline were orally daily administered one week before stress induction and extended up to ten weeks. Behavioral, brain biochemical tests and serum magnesium were assessed at the end. The study revealed significant change in the combined group on behavioral tests; forced swim test, elevated plus maze and saccharin preference test when compared to barley extract group. Furthermore, there was significant reduction in brain malondialdehyde level, no significant change in brain nitric oxide level, while significant increase in serum magnesium level was noticed. Whereas, the barley extract group recorded a lowest significant improvement in behavioral, brain and serum biochemical tests. It could be concluded that barley and venlafaxine together had muffled the oxidant stress and increased brain serotonin, serum magnesium level that might had a crucial role in experimental induced chronic mild stress in rats.

Anterior olfactory organ removal produces anxiety-like behavior and increases spontaneous neuronal firing rate in basal amygdala

Some chemical cues may produce signs of anxiety and fear mediated by amygdala nuclei, but unknown is the role of two anterior olfactory epithelial organs, the septal and vomeronasal organs (SO-VNOs). The effects of SO-VNO removal were explored in different groups of Wistar rats using two complementary approaches: (i) the assessment of neuronal firing rate in basal and medial amygdala nuclei and (ii) behavioral testing. Fourteen days after SO-VNO removal, spontaneous activity in basal and medial amygdala nuclei in one group was determined using single-unit extracellular recordings. A separate group of rats was tested in the elevated plus maze, social interaction test, and open field test. Compared with sham-operated and intact control rats, SO-VNO removal produced a higher neuronal firing rate in the basal amygdala but not medial amygdala. In the behavioral tests, SO-VNO removal increased signs of anxiety in the elevated plus maze, did not alter locomotion, and increased self-directed behavior, reflecting anxiety-like behavior. Histological analysis showed neuronal destruction in the accessory olfactory bulb but not anterior olfactory nucleus in the SO-VNO group. The present results suggest the participation of SO-VNO/accessory olfactory bulb/basal amygdala relationships in the regulation of anxiety through a process of disinhibition.

Sexually dimorphic neurons in the ventromedial hypothalamus govern mating in both sexes and aggression in males

Sexual dimorphisms in the brain underlie behavioral sex differences, but the function of individual sexually dimorphic neuronal populations is poorly understood. Neuronal sexual dimorphisms typically represent quantitative differences in cell number, gene expression, or other features, and it is unknown whether these dimorphisms control sex-typical behavior exclusively in one sex or in both sexes. The progesterone receptor (PR) controls female sexual behavior, and we find many sex differences in number, distribution, or projections of PR-expressing neurons in the adult mouse brain. Using a genetic strategy we developed, we have ablated one such dimorphic PR-expressing neuronal population located in the ventromedial hypothalamus (VMH). Ablation of these neurons in females greatly diminishes sexual receptivity. Strikingly, the corresponding ablation in males reduces mating and aggression. Our findings reveal the functions of a molecularly defined, sexually dimorphic neuronal population in the brain. Moreover, we show that sexually dimorphic neurons can control distinct sex-typical behaviors in both sexes.

Mathematical methods to model rodent behavior in the elevated plus-maze

The elevated plus maze is a widely used experimental test to study anxiety-like rodent behavior. It is made of four arms, two open and two closed, connected at a central area forming a plus shaped maze. The whole apparatus is elevated 50 cm from the floor. The anxiety of the animal is usually assessed by the number of entries and duration of stay in each arm type during a 5-min period. Different mathematical methods have been proposed to model the mechanisms that control the animal behavior in the maze, such as factor analysis, statistical inference on Markov chains and computational modeling. In this review we discuss these methods and propose possible extensions of them as a direction for future research.

Neurotransmitter switching in the adult brain regulates behavior

Neurotransmitters have been thought to be fixed throughout life, but whether sensory stimuli alter behaviorally relevant transmitter expression in the mature brain is unknown. We found that populations of interneurons in the adult rat hypothalamus switched between dopamine and somatostatin expression in response to exposure to short- and long-day photoperiods. Changes in postsynaptic dopamine receptor expression matched changes in presynaptic dopamine, whereas somatostatin receptor expression remained constant. Pharmacological blockade or ablation of these dopaminergic neurons led to anxious and depressed behavior, phenocopying performance after exposure to the long-day photoperiod. Induction of newly dopaminergic neurons through exposure to the short-day photoperiod rescued the behavioral consequences of lesions. Natural stimulation of other sensory modalities may cause changes in transmitter expression that regulate different behaviors.

Individual differences in the effects of chronic stress on memory: behavioral and neurochemical correlates of resiliency

Chronic stress has been shown to impair memory, however, the extent to which memory can be impaired is often variable across individuals. Predisposed differences in particular traits, such as anxiety, may reveal underlying neurobiological mechanisms that could be driving individual differences in sensitivity to stress and, thus, stress resiliency. Such pre-morbid characteristics may serve as early indicators of susceptibility to stress. Neuropeptide Y (NPY) and enkephalin (ENK) are neurochemical messengers of interest implicated in modulating anxiety and motivation circuitry; however, little is known about how these neuropeptides interact with stress resiliency and memory. In this experiment, adult male rats were appetitively trained to locate sugar rewards in a motivation-based spatial memory task before undergoing repeated immobilization stress and then being tested for memory retention. Anxiety-related behaviors, among other characteristics, were monitored longitudinally. Results indicated that stressed animals which showed little to no impairments in memory post-stress (i.e., the more stress-resilient individuals) exhibited lower anxiety levels prior to stress when compared to stressed animals that showed large deficits in memory (i.e., the more stress-susceptible individuals). Interestingly, all stressed animals, regardless of memory change, showed reduced body weight gain as well as thymic involution, suggesting that the effects of stress on metabolism and the immune system were dissociated from the effects of stress on higher cognition, and that stress resiliency seems to be domain-specific rather than a global characteristic within an individual. Neurochemical analyses revealed that NPY in the hypothalamus and amygdala and ENK in the nucleus accumbens were modulated differentially between stress-resilient and stress-susceptible individuals, with elevated expression of these neuropeptides fostering anxiolytic and pro-motivation function, thus driving cognitive resiliency in a domain-specific manner. Findings suggest that such neurochemical markers may be novel targets for pharmacological interventions that can serve to prevent or ameliorate the negative effects of stress on memory.

Influence of chronic moderate sleep restriction and exercise training on anxiety, spatial memory, and associated neurobiological measures in mice

Sleep deprivation can have deleterious effects on cognitive function and mental health. Moderate exercise training has myriad beneficial effects on cognition and mental health. However, physiological and behavioral effects of chronic moderate sleep restriction and its interaction with common activities, such as moderate exercise training, have received little investigation. The aims of this study were to examine the effects of chronic moderate sleep restriction and moderate exercise training on anxiety-related behavior, spatial memory, and neurobiological correlates in mice. Male mice were randomized to one of four 11-week treatments in a 2 [sleep restriction (∼4h loss/day) vs. ad libitum sleep] × 2 [exercise (1h/day/6 d/wk) vs. sedentary activity] experimental design. Anxiety-related behavior was assessed with the elevated-plus maze, and spatial learning and memory were assessed with the Morris water maze. Chronic moderate sleep restriction did not alter anxiety-related behavior, but exercise training significantly attenuated anxiety-related behavior. Spatial learning and recall, hippocampal cell activity (i.e., number of c-Fos positive cells), and brain derived neurotrophic factor were significantly lower after chronic moderate sleep restriction, but higher after exercise training. Further, the benefit of exercise training for some memory variables was evident under normal sleep, but not chronic moderate sleep restriction conditions. These data indicate clear detrimental effects of chronic moderate sleep restriction on spatial memory and that the benefits of exercise training were impaired after chronic moderate sleep restriction.

Neurobehavioral characterization of Endonuclease G knockout mice reveals a new putative molecular player in the regulation of anxiety

Endonuclease G (EndoG) has been largely related with a role in the modulation of a caspase-independent cell death pathway in many cellular systems. However, whether this protein plays a specific role in the brain remains to be elucidated. Here we have characterized the behavioral phenotype of EndoG(-/-) null mice and the expression of the nuclease among brain regions. EndoG(-/-) mice showed normal neurological function, learning, motor coordination and spontaneous behaviors. However, these animals displayed lower activity in a running wheel and, strikingly, they were consistently less anxious compared to EndoG(+/+) mice in different tests for anxiety such as plus maze and dark-light test. We next evaluated the expression of EndoG in different brain regions of wild type mice and found that it was expressed in all over but specially enriched in the striatum. Further, subcellular biochemical experiments in neocortical samples from wild type mice revealed that EndoG is localized in pre-synaptic compartments but not in post-synaptic compartments. Altogether these findings suggest that EndoG could play a highly specific role in the regulation of anxiety by modulating synaptic components.

Vulnerability imposed by diet and brain trauma for anxiety-like phenotype: implications for post-traumatic stress disorders

Mild traumatic brain injury (mTBI, cerebral concussion) is a risk factor for the development of psychiatric illness such as posttraumatic stress disorder (PTSD). We sought to evaluate how omega-3 fatty acids during brain maturation can influence challenges incurred during adulthood (transitioning to unhealthy diet and mTBI) and predispose the brain to a PTSD-like pathobiology. Rats exposed to diets enriched or deficient in omega-3 fatty acids (n-3) during their brain maturation period, were transitioned to a western diet (WD) when becoming adult and then subjected to mTBI. TBI resulted in an increase in anxiety-like behavior and its molecular counterpart NPY1R, a hallmark of PTSD, but these effects were more pronounced in the animals exposed to n-3 deficient diet and switched to WD. The n-3 deficiency followed by WD disrupted BDNF signaling and the activation of elements of BDNF signaling pathway (TrkB, CaMKII, Akt and CREB) in frontal cortex. TBI worsened these effects and more prominently in combination with the n-3 deficiency condition. Moreover, the n-3 deficiency primed the immune system to the challenges imposed by the WD and brain trauma as evidenced by results showing that the WD or mTBI affected brain IL1β levels and peripheral Th17 and Treg subsets only in animals previously conditioned to the n-3 deficient diet. These results provide novel evidence for the capacity of maladaptive dietary habits to lower the threshold for neurological disorders in response to challenges.

The β2 nicotinic acetylcholine receptor subunit differentially influences ethanol behavioral effects in the mouse

The high co-morbidity between alcohol (ethanol) and nicotine abuse suggests that nicotinic acetylcholine receptors (nAChRs), thought to underlie nicotine dependence, may also be involved in alcohol dependence. The β2* nAChR subtype serves as a potential interface for these interactions since they are the principle mediators of nicotine dependence and have recently been shown to modulate some acute responses to ethanol. Therefore, the aim of this study was to more fully characterize the role of β2* nAChRs in ethanol-responsive behaviors in mice after acute exposure to the drug. We conducted a battery of tests in mice lacking the β2* coding gene (Chrnb2) or pretreated with a selective β2* nAChR antagonist for a range of ethanol-induced behaviors including locomotor depression, hypothermia, hypnosis, and anxiolysis. We also tested the effect of deletion on voluntary escalated ethanol consumption in an intermittent access two-bottle choice paradigm to determine the extent of these effects on drinking behavior. Our results showed that antagonism of β2* nAChRs modulated some acute behaviors, namely by reducing recovery time from hypnosis and enhancing the anxiolytic-like response produced by acute ethanol in mice. Chrnb2 deletion had no effect on ethanol drinking behavior, however. We provide further evidence that β2* nAChRs have a measurable role in mediating specific behavioral effects induced by acute ethanol exposure without affecting drinking behavior directly. We conclude that these receptors, along with being key components in nicotine dependence, may also present viable candidates in the discovery of the molecular underpinnings of alcohol dependence.

Preliminary study: effects of social instability stress on depressive behaviours in ovariectomised rats

BACKGROUND

Depression is one of the common post-menopausal symptoms. In addition to estrogen deficiency, social instability stress may contribute as an additional underlying factor in the development of depressive behaviour in females. Therefore, this study was aimed at examining the influence of social instability stress on depressive behaviour in ovariectomized rats.

METHODS

The rats were divided into four groups (n = 5 per group); (i) sham-operated control without stress, (ii) sham-operated control with stress, (iii) ovariectomized without stress, and (iv) ovariectomized with stress. These rats were subjected to social instability stress procedures for 15 days prior to an enforced swimming test. Struggling, immobility, and swimming times were recorded promptly.

RESULTS

The results were analysed using the one-way analysis of variance (ANOVA) and a P value of < 0.05 was considered as significant. The mean durations of struggling, immobility, and swimming behaviour were significantly distinct among the four groups. Ovariectomized rats exhibited a substantial decrease in struggling and swimming behaviour, and an increase in immobility behaviour in comparison with the sham-operated controls (P < 0.05). Ovariectomized rats with stress displayed a supplementary decrease in struggling and swimming behaviour as well as an advanced increase in immobility behaviour, compared to sham-operated controls with or without stress (P < 0.05).

CONCLUSION

In summary, these findings suggest that ovariectomized rats encountered an augmented amount of depressive behaviour following social instability stress.

Ingestion of Mycobacterium vaccae decreases anxiety-related behavior and improves learning in mice

Coevolution of microbes and their hosts has resulted in the formation of symbiotic relationships that enable animals to adapt to their environments and protect themselves against pathogens. Recent studies show that contact with tolerogenic microbes is important for the proper functioning of immunoregulatory circuits affecting behavior, emotionality and health. Few studies have examined the potential influence of ambient bacteria, such as Mycobacterium vaccae on the gut-brain-microbiota axis. In this preliminary research, we show that mice fed live M. vaccae prior to and during a maze learning task demonstrated a reduction in anxiety-related behaviors and maze completion time, when tested at three maze difficulty levels over 12 trials for four weeks. Treated mice given M. vaccae in their reward completed the maze twice as fast as controls, and with reduced anxiety-related behaviors. In a consecutive set of 12 maze trials without M. vaccae exposure, treated mice continued to run the maze faster for the first three trials, and with fewer errors overall, suggesting a treatment persistence of about one week. Following a three-week hiatus, a final maze run revealed no differences between the experimentals and controls. Additionally, M. vaccae-treated mice showed more exploratory head-dip behavior in a zero maze, and M. vaccae treatment did not appear to affect overall activity levels as measured by activity wheel usage. Collectively, our results suggest a beneficial effect of naturally delivered, live M. vaccae on anxiety-related behaviors and maze performance, supporting a positive role for ambient microbes in the immunomodulation of animal behavior.

Treatment with an anti-CD11d integrin antibody reduces neuroinflammation and improves outcome in a rat model of repeated concussion

Background

Concussions account for the majority of traumatic brain injuries (TBI) and can result in cumulative damage, neurodegeneration, and chronic neurological abnormalities. The underlying mechanisms of these detrimental effects remain poorly understood and there are presently no specific treatments for concussions. Neuroinflammation is a major contributor to secondary damage following more severe TBI, and recent findings from our laboratory suggest it may be involved in the cumulative properties of repeated concussion. We previously found that an anti-CD11d monoclonal antibody that blocks the CD11d/CD18 integrin and adhesion molecule interaction following severe experimental TBI reduces neuroinflammation, oxidative activity, and tissue damage, and improves functional recovery. As similar processes may be involved in repeated concussion, here we studied the effects of the anti-CD11d treatment in a rat model of repeated concussion.

Methods

Rats were treated 2 h and 24 h after each of three repeated mild lateral fluid percussion injuries with either the CD11d antibody or an isotype-matched control antibody, 1B7. Injuries were separated by a five-day inter-injury interval. After the final treatment and either an acute (24 to 72 h post-injury) or chronic (8 weeks post-injury) recovery period had elapsed, behavioral and pathological outcomes were examined.

Results

The anti-CD11d treatment reduced neutrophil and macrophage levels in the injured brain with concomitant reductions in lipid peroxidation, astrocyte activation, amyloid precursor protein accumulation, and neuronal loss. The anti-CD11d treatment also improved outcome on tasks of cognition, sensorimotor ability, and anxiety.

Conclusions

These findings demonstrate that reducing inflammation after repeated mild brain injury in rats leads to improved behavioral outcomes and that the anti-CD11d treatment may be a viable therapy to improve post-concussion outcomes.

AAV-based gene therapy prevents neuropathology and results in normal cognitive development in the hyperargininemic mouse

Complete arginase I deficiency is the least severe urea cycle disorder, characterized by hyperargininemia and infrequent episodes of hyperammonemia. Patients suffer from neurological impairment with cortical and pyramidal tract deterioration, spasticity, loss of ambulation, and seizures, and is associated with intellectual disability. In mice, onset is heralded by weight loss beginning around day 15; gait instability follows progressing to inability to stand and development of tail tremor with seizure-like activity and death. Here we report that hyperargininemic mice treated neonatally with an adeno-associated virus expressing arginase and followed long-term lack any presentation consistent with brain dysfunction. Behavioral and histopathological evaluation demonstrated that treated mice are indistinguishable from littermates and that putative compounds associated with neurotoxicity are diminished. In addition, treatment results in near complete resolution of metabolic abnormalities early in life; however there is the development of some derangement later with decline in transgene expression. Ammonium challenging revealed that treated mice are affected by exogenous loading much greater than littermates. These results demonstrate that AAV-based therapy for hyperargininemia is effective and prevents development of neurological abnormalities and cognitive dysfunction in a mouse model of hyperargininemia; however nitrogen challenging reveals that these mice remain impaired in the handling of waste nitrogen.

The active alkaloids of Gelsemium elegans Benth. are potent anxiolytics

RATIONALE

An increasing number of herbal products has been introduced to treat anxiety and depression. Gelsemium elegans Benth (G. elegans) is a well-known herbal plant in Asia. Four major alkaloids (gelsemine, koumine, gelsevirine, and gelsenicine) have been isolated from G. elegans. Recently, interest has arisen to investigate the pharmaceutical potential of G. elegans alkaloids in the context of neuropsychopharmacology.

OBJECTIVES

We investigated whether G. elegans alkaloids are capable of producing anxiolytic and antidepressant effects in mouse models. In particular, we examined whether the anxiolytic action of G. elegans alkaloids is due to the agonist effects of glycine receptor in the brain.

METHODS

Two mouse models (elevated plus-maze and light-dark transition model) were used to examine potential anxiolytic effects. Forced swim test and tail suspension test were used to test the antidepressive action of G. elegans alkaloids. Moreover, we also explored the anxiolytic mechanisms of G. elegans alkaloids by intracerebroventricular administration of strychnine, an antagonist of glycine receptor, in the elevated plus-maze.

RESULTS

Gelsemine, koumine, and gelsevirine, but not gelsenicine, exhibited potent anxiolytic effects in the two anxiety models. None of the four G. elegans alkaloids exerted antidepressant effects in the two depression models. None of G. elegans alkaloids impaired spontaneous motor activities. The intracerebroventricular administration of strychnine significantly antagonized the anxiolytic effects of gelsemine, koumine, and gelsevirine administrated subcutaneously.

CONCLUSIONS

Gelsemine, koumine, and gelsevirine could be developed as the treatment of anxiety-related disorders in human patients. Their anxiolytic mechanism may be involved in the agonist action of glycine receptor in the brain.

Yohimbine anxiogenesis in the elevated plus maze requires hindbrain noradrenergic neurons that target the anterior ventrolateral bed nucleus of the stria terminalis

The α2 adrenergic receptor antagonist yohimbine (YO) increases transmitter release from noradrenergic (NA) terminals in cortical and subcortical brain regions, including the bed nucleus of the stria terminalis (BST). YO activates the hypothalamic-pituitary-adrenal (HPA) stress axis and is potently anxiogenic in rats and humans. We previously reported that hindbrain NA neurons within the caudal nucleus of the solitary tract (NST-A2/C2) and ventrolateral medulla (VLM-A1/C1) that innervate the anterior ventrolateral (vl)BST contribute to the ability of YO to activate the HPA stress axis in rats. To determine whether the same NA pathway also contributes to YO-induced anxiogenesis in the elevated plus maze (EPMZ), a selective saporin ribotoxin conjugate (dopamine beta hydroxylase conjugated to saporin toxin, DSAP) was microinjected bilaterally into the anterior vlBST to destroy its NA inputs. Sham-lesioned controls were microinjected with vehicle. Two experiments were conducted to determine DSAP lesion effects on EPMZ behavior. DSAP lesions did not alter maze behavior in rats after intraperitoneal saline, and did not alter the significant effect of prior maze experience to reduce exploratory and open arm maze activities. However, in maze-naïve rats, DSAP lesions abolished YO anxiogenesis in the EPMZ. Post-mortem immunocytochemical analyses confirmed that DSAP consistently ablated caudal NST-A2/C2 and VLM-A1/C1 neurons that innervate the anterior vlBST. DSAP lesions did not destroy non-NA inputs to the anterior vlBST, and produced inconsistent cell loss within the pontine locus coeruleus (A6 cell group) that was unrelated to YO anxiogenesis. Thus, the ability of YO to increase anxiety-like behavior in the EPMZ depends on hindbrain NA neurons that target the anterior vlBST.

Central relaxin-3 receptor (RXFP3) activation decreases anxiety- and depressive-like behaviours in the rat

Relaxin-3 is a recently discovered neuropeptide and the results of earlier anatomical and pharmacological studies suggest it plays a physiological role in modulating functions such as arousal, learning and memory, food intake and neuroendocrine homeostasis. Relaxin-3 is also postulated to modulate affective behaviour, based on high densities of the relaxin-3 G-protein coupled receptor (RXFP3) in brain areas involved in stress and mood/anxiety, including the central amygdala, bed nucleus of the stria terminalis and hypothalamic paraventricular nucleus (PVN); and strong activation of relaxin-3 neurons by stressors, via activation of corticotropin-releasing factor receptor-1 (CRF1). This study assessed the effect of central administration of a newly developed RXFP3-selective agonist, on anxiety- and depressive-like behaviour in rats. Adult, male Sprague-Dawley rats administered 5 μg [R3A(11-24,C15→A)B] (referred to as RXFP3-A2), intracerebroventricularly, demonstrated decreased anxiety-like behaviour in the light-dark box and elevated plus maze, but not in the open field. Notably, in the repeat forced swim test, central RXFP3-A2 administration decreased immobility in rats that had been subjected to the 'stress' of former exposure to the anxiety tests, but not in experimentally naïve rats. These data implicate relaxin-3/RXFP3 signalling in the modulation of effects of acute (anxiety) and cumulative (depression) neurogenic stressors on behaviour; and suggest a potential for RXFP3 agonists as anxiolytic and anti-depressant agents. In addition, our results demonstrate that exposure of adult Sprague-Dawley rats to tests of anxiety-like behaviour (∼10-14 days prior) can significantly increase immobility time in the repeat forced swim test.

Involvement of the ventral tegmental area in a rodent model of post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is an anxiety disorder of considerable prevalence in individuals who have experienced a traumatic event. Studies of the neural substrate of this disorder have focused on the role of areas such as the hippocampus, the amygdala and the medial prefrontal cortex. We show that the ventral tegmental area (VTA), which directly modulates these areas, is part of this circuitry. Using a rat model of PTSD, we show that a brief but intense foot shock followed by three brief reminders can cause long-term behavioral changes as shown by anxiety-like, nociception, and touch-sensitivity tests. We show that an intraperitoneal injection of a dopamine (DA) antagonist or a bilateral inactivation of the VTA administered immediately before the traumatic event decrease the occurrence or intensity of these behavioral changes. Furthermore, we show that there is a significant decrease of baseline VTA dopaminergic but not GABAergic cell firing rates 2 weeks after trauma. Our data suggest that VTA DA neurons undergo long-term physiological changes after trauma and that this brain area is a crucial part of the circuits involved in PTSD symptomatology.

Toxoplasma gondii infection, from predation to schizophrenia: can animal behaviour help us understand human behaviour?

We examine the role of the protozoan Toxoplasma gondii as a manipulatory parasite and question what role study of infections in its natural intermediate rodent hosts and other secondary hosts, including humans, may elucidate in terms of the epidemiology, evolution and clinical applications of infection. In particular, we focus on the potential association between T. gondii and schizophrenia. We introduce the novel term 'T. gondii-rat manipulation-schizophrenia model' and propose how future behavioural research on this model should be performed from a biological, clinical and ethically appropriate perspective.

Chemical composition and anxiolytic evaluation of Achillea Wilhelmsii C. Koch essential oil in rat

Herbal based remedies are used worldwide to treat psychiatric disorders. The aim of this study was to analyse the essential oil composition of Achillea Wilhemsii C. Koch (Asteraceae) and to evaluate its anxiolytic effects in the elevated plus maze (EPM) model of anxiety in rat. Gas chromatography/mass spectrometry (GC/MS) analysis of the essential oil showed that the main compounds of the oil were p-ocimen (23%), 1, 8-cineole (20.8%) and carvone (19.13%). The EPM results showed that 1 mg/kg (i.p.) of the oil significantly (P<0.05) increased the percentage of the time spent and the number of entries in the open arms of the maze while it did not change the total number of entries in the maze arms. These effects were not reversed with 2 mg/kg flumazenil and 5 mg/kg naloxone. We concluded that a minimum dose of 1 mg/kg of the oil has anxiolytic effects which are not probably mediated through GABA and opioid receptors.

Global cerebral ischemia: synaptic and cognitive dysfunction

Cardiopulmonary arrest is one of the leading causes of death and disability, primarily occurring in the aged population. Numerous global cerebral ischemia animal models induce neuronal damage similar to cardiac arrest. These global cerebral ischemia models range from vessel occlusion to total cessation of cardiac function, both of which have allowed for the investigation of this multifaceted disease and detection of numerous agents that are neuroprotective. Synapses endure a variety of alterations after global cerebral ischemia from the resulting excitotoxicity and have been a major target for neuroprotection; however, neuroprotective agents have proven unsuccessful in clinical trials, as neurological outcomes have not displayed significant improvements in patients. A majority of these neuroprotective agents have specific neuronal targets, where the success of future neuroprotective agents may depend on non-specific targets and numerous cognitive improvements. This review focuses on the different models of global cerebral ischemia, neuronal synaptic alterations, synaptic neuroprotection and behavioral tests that can be used to determine deficits in cognitive function after global cerebral ischemia.

Anxiolytic effects of flavonoids in animal models of posttraumatic stress disorder

The dysregulation of the serotonergic system has long been recognized as an important factor underlying the pathophysiology of PTSD. To date, SSRIs have already been established as the firstline pharmacotherapeutic agents for treating acute and chronic PTSD. However, SSRIs largely have several disadvantages which limit their utility. Our previous study has also shown that administration of the total flavonoids, isolated from the extract of Xiaobuxin-Tang (XBXT, mild mind-easing decoction), comprising four Chinese medicines including Haematitum, Flos Inulae, Folium Phyllostachydis Henonis, and Semen Sojae Preparatum, exerted significant antidepressant-like effect in chronically mildly stressed rats, possibly mediated by serotonergic activation. Since the central serotonergic dysfunction is an important and well-known cause mediating the pathophysiology of trauma-related symptoms in PTSD, it is reasonable to predict that flavonoids may exert therapeutic effects on PTSD in animal models. Therefore, the present study aims to examine the effect of flavonoids in alleviating the enhanced anxiety and fear response induced in two PTSD animal models. Ser, an SSRI, was administered as a positive control. Furthermore, the changes of brain monoaminergic neurotransmitters after chronic flavonoids administration have also been assessed in SPS-treated rats.

Stress-induced epigenetic transcriptional memory of acetylcholinesterase by HDAC4

Stress induces long-lasting changes in neuronal gene expression and cholinergic neurotransmission, but the underlying mechanism(s) are incompletely understood. Here, we report that chromatin structure and histone modifications are causally involved in this transcriptional memory. Specifically, the AChE gene encoding the acetylcholine-hydrolyzing enzyme acetylcholinesterase is known to undergo long-lasting transcriptional and alternative splicing changes after stress. In mice subjected to stress, we identified two alternative 5' exons that were down-regulated after stress in the hippocampus, accompanied by reduced acetylation and elevated trimethylation of H3K9 at the corresponding promoter. These effects were reversed completely by daily administration of the histone deacetylase (HDAC) inhibitor sodium butyrate for 1 wk after stress. H3K9 hypoacetylation was associated with a selective, sodium butyrate-reversible promoter accumulation of HDAC4. Hippocampal suppression of HDAC4 in vivo completely abolished the long-lasting AChE-related and behavioral stress effects. Our findings demonstrate long-lasting stress-inducible changes in AChE's promoter choices, identify the chromatin changes that support this long-term transcriptional memory, and reveal HDAC4 as a mediator of these effects in the hippocampus.

Effects of kisspeptin-13 on the hypothalamic-pituitary-adrenal axis, thermoregulation, anxiety and locomotor activity in rats

Kisspeptin is a mammalian amidated neurohormone, which belongs to the RF-amide peptide family and is known for its key role in reproduction. However, in contrast with the related members of the RF-amide family, little information is available regarding its role in the stress-response. With regard to the recent data suggesting kisspeptin neuronal projections to the paraventricular nucleus, in the present experiments we investigated the effect of kisspeptin-13 (KP-13), an endogenous derivative of kisspeptin, on the hypothalamus-pituitary-adrenal (HPA) axis, motor behavior and thermoregulatory function. The peptide was administered intracerebroventricularly (icv.) in different doses (0.5-2 μg) to adult male Sprague-Dawley rats, the behavior of which was then observed by means of telemetry, open field and elevated plus maze tests. Additionally, plasma concentrations of corticosterone were measured in order to assess the influence of KP-13 on the HPA system. The effects on core temperature were monitored continuously via telemetry. The results demonstrated that KP-13 stimulated the horizontal locomotion (square crossing) in the open field test and decreased the number of entries into and the time spent in the open arms during the elevated plus maze tests. The peptide also caused marked elevations in the spontaneous locomotor activity and the core temperature recorded by the telemetric system, and significantly increased the basal corticosterone level. In conclusion, our data indicate that icv. administered KP-13 stimulates the HPA axis, induces hyperthermia, activates motor behavior and causes anxiety in rats.

Changes in behaviors of male C57BL/6J mice across adult life span and effects of dietary restriction

Behavioral analysis is a high-end read-out of aging impact on an organism, and here, we have analyzed behaviors in 4-, 22-, and 28-month-old male C57BL/6J with a broad range of tests. For comparison, a group of 28-month-old males maintained on dietary restriction (DR) was included. The most conspicuous alteration was the decline in exploration activity with advancing age. Aging also affected other behaviors such as motor skill acquisition and grip strength, in contrast to latency to thermal stimuli and visual placement which were unchanged. Object recognition tests revealed intact working memory at 28 months while memory recollection was impaired already at 22 months. Comparison with female C57BL/6J (Fahlström et al., Neurobiol Aging 32:1868-1880, 2011) revealed that alterations in aged males and females are similar and that several of the behavioral indices correlate with age in both sexes. Moreover, we examined if behavioral indices in 22-month-old males could predict remaining life span as suggested in the study by Ingram and Reynolds (Exp Aging Res 12(3):155-162, 1986) and found that exploratory activity and motor skills accounted for up to 65% of the variance. Consistent with that a high level of exploratory activity and preserved motor capacity indicated a long post-test survival, 28-month-old males maintained on DR were more successful in such tests than ad libitum fed age-matched males. In summary, aged C57BL/6J males are marked by a reduced exploratory activity, an alteration that DR impedes. In light of recently published data, we discuss if a diminishing drive to explore may associate with aging-related impairment of central aminergic pathways.

Environmental enrichment upregulates micro-RNA-183 and alters acetylcholinesterase splice variants to reduce anxiety-like behavior in the little Indian field mouse (Mus booduga)

Environmental enrichment (EE) has an influential role in reducing behavioral reactivity to stress. We previously observed that EE reduces the anxiety-like behavior in the field mouse Mus booduga accompanied by a reduction in the expression of molecules involved in the stress pathway. In this study, we demonstrate the effect of different housing condition on regulation of micro-RNA-183-SC35-mediated splicing of acetylcholinesterase (AChE). Adult male M. booduga were captured from an agricultural field and housed under nonenriched standard conditions (SC) for 7 days and considered as directly from the wild (DW). On day 8, individuals were randomly assigned to three groups; DW, SC, and EE. The DW group's anxiety-like behavior was assessed in the elevated plus maze (EPM) and open field test (OFT). The SC and EE groups were transferred to their respective conditions and housed for another 30 days. The mice housed in EE showed less anxiety-like behavior on EPM and in OFT compared with DW and SC mice. Interestingly, miR-183 expression was increased following exposure to EPM in EE mice but not in SC mice. Subsequently, the upregulated miR-183 expression suppresses the SC35 expression and shifting of splicing from AChE-S (synaptic) to AChE-R (read-through) form, whereas standard housing condition downregulate miR-183 and induces the splicing of AChE. The upregulated AChE-R form possibly terminates ACh transmission, which is reflected in the level of anxiety-like behavior. Overall, the present study suggests that EE effectively regulates the miR-183 pathway to reduce anxiety-like behavior.

The neuro-behavioral profile in rats after subarachnoid hemorrhage

Despite significant advancements in the understanding of the pathophysiological mechanisms of subarachnoid hemorrhage (SAH), little is known about the emotional consequences. The primary goal of this study was to describe the locomotor and behavioral patterns in rats following both a single-injection and double-injection model of SAH. In 48 rats, SAH was induced by injecting 0.3 ml of autologous arterial blood into the cisterna magnum (single-hemorrhagic model). In 24 of these rats, post-SAH vasospasm was induced by a repeated injection of blood into the cisterna magnum 24h later (double-hemorrhagic model). In 24 additional rats, 0.3 ml of saline was injected into the cisterna magnum (sham group). Neurological performance was assessed at 24, 48 h, 1, 2 and 3 weeks after SAH. Four behavioral tests were performed for 3 weeks after SAH for the duration of 6 consequent days, in the following order: open field test, sucrose preference test, elevated plus maze test and forced swimming test. Following both, a single and double-hemorrhagic models of SAH, rats were found to have significant behavioral abnormalities on the open field test, sucrose preference test, elevated plus maze test, and forced swimming test. A more prominent disability was found in rats that underwent the double-hemorrhagic model of SAH than rats that underwent the single-hemorrhagic model. Both a single and double injection model of rats SAH are associated with significant behavioral disturbances including locomotor abnormalities, depressive behavior and increased anxiety, even as early as 3 weeks after SAH.

Psychological stress on female mice diminishes the developmental potential of oocytes: a study using the predatory stress model

Although the predatory stress experimental protocol is considered more psychological than the restraint protocol, it has rarely been used to study the effect of psychological stress on reproduction. Few studies exist on the direct effect of psychological stress to a female on developmental competence of her oocytes, and the direct effect of predatory maternal stress on oocytes has not been reported. In this study, a predatory stress system was first established for mice with cats as predators. Beginning 24 h after injection of equine chorionic gonadotropin, female mice were subjected to predatory stress for 24 h. Evaluation of mouse responses showed that the predatory stress system that we established increased anxiety-like behaviors and plasma cortisol concentrations significantly and continuously while not affecting food and water intake of the mice. In vitro experiments showed that whereas oocyte maturation and Sr(2+) activation or fertilization were unaffected by maternal predatory stress, rate of blastocyst formation and number of cells per blastocyst decreased significantly in stressed mice compared to non-stressed controls. In vivo embryo development indicated that both the number of blastocysts recovered per donor mouse and the average number of young per recipient after embryo transfer of blastocysts with similar cell counts were significantly lower in stressed than in unstressed donor mice. It is concluded that the predatory stress system we established was both effective and durative to induce mouse stress responses. Furthermore, predatory stress applied during the oocyte pre-maturation stage significantly impaired oocyte developmental potential while exerting no measurable impact on nuclear maturation, suggesting that cytoplasmic maturation of mouse oocytes was more vulnerable to maternal stress than nuclear maturation.

Neonatal whisker clipping alters behavior, neuronal structure and neural activity in adult rats

Early experience plays critical roles during the development of sensory systems. For example, neonatal surgical manipulations of the whiskers in rodents lead to altered neural activity and behaviors later in life. However, while surgical procedures damage the sensory pathway; it is hard to examine the impact of whisker deprivation on adult animals. To address this issue, we performed a neonatal whisker clipping (WC0-3) paradigm, a non-invasive procedure, from the day of birth (P0) to postnatal day (P) 3, and examined behavioral performances in their adult age. With fully regrown whiskers, the WC0-3 rats exhibited shorter crossable distance than controls in a gap-crossing task, suggesting a defect in their whisker-specific tactile function. In their somatosensory cortex, the layer IV spiny stellate neurons had reduced dendritic complexity and spine density. After exploration in a novel environment, the expression of an activity-dependent immediate early gene, c-fos, increased dramatically in the somatosensory cortex. However, in WC0-3 rats, the number of c-Fos positive cells was less than those in control rats, indicating a fault in transducing sensory-related neural activity between cortical layers in WC0-3 rats. Together, our results demonstrate the roles of early tactile experience on the establishment of layer-specific excitatory connection in the barrel cortex. Early sensory insufficiency would leave long-lasting functional deficits in the sensory system.

Increased nociceptive sensitivity and nociceptin/orphanin FQ levels in a rat model of PTSD

BACKGROUND

Clinical studies indicate that post-traumatic stress disorder (PTSD) frequently shares co-morbidity with chronic pain. Although in animals acute stress-induced antinociception is well documented, the effect of PTSD-like stress on nociceptive sensitivity is unclear. Though a few studies measured nociceptive responses at a single time point, no studies have examined changes in nociceptive sensitivity over time following exposure to PTSD-like stress. Nociceptin/orphanin FQ (N/OFQ), an endogenous ligand for the N/OFQ peptide (NOP) receptor, modulates various biological functions in the central nervous system that are affected by PTSD, including nociceptive sensitivity, stress and anxiety, learning and memory.

RESULTS

The present study examined thermal and mechanical nociceptive sensitivity in male Sprague Dawley rats between 7 and 28 days after single-prolonged stress (SPS), an established animal model for PTSD. Rat paw withdrawal thresholds (PWT) to von Frey and paw withdrawal latencies (PWL) to radiant heat stimuli, respectively, dramatically decreased as early as 7 days after initiation of SPS and lasted the length of the study, 28 days. In addition, N/OFQ levels increased in cerebrospinal fluid (CSF; on days 9, 14 and 28) and serum (day 28), while levels of circulating corticosterone (CORT) decreased 28 days after initiation of SPS. SPS exposure induced anxiety-like behavior and enhanced inhibition of the hypothalamo-pituitary-adrenal (HPA) axis, as previously reported for this model.

CONCLUSIONS

Our results demonstrate that SPS induces the development of persistent mechanical allodynia and thermal hyperalgesia that is accompanied by increased N/OFQ content in the CSF, and eventually, in serum. These findings suggest a link between N/OFQ and the development of hyperalgesia and allodynia in a rat model of PTSD.

Morphine-induced anxiolytic-like effect in morphine-sensitized mice: involvement of ventral hippocampal nicotinic acetylcholine receptors

In the present study, the effects of repeated intra-ventral hippocampal (intra-VH) microinjections of nicotinic acetylcholine receptor agonist or antagonist on morphine-induced anxiolytic-like behavior were investigated in morphine-sensitized mice using elevated plus-maze. Intraperitoneal (i.p.) administration of different doses of morphine (5, 7.5 and 10mg/kg) increased the percentage of open arm time (%OAT), open arm entries (%OAE), but not locomotor activity, indicating an anxiolytic-like response to morphine. The maximum response was obtained by 7.5mg/kg of the opioid. The anxiety-like behavior which was induced by a lower dose of morphine (5mg/kg) was significantly increased in mice that had previously received once daily injections of morphine (10 and 20mg/kg, i.p.) for 3 days. It should be considered that this treatment also increased locomotor activity in morphine-sensitized mice. Furthermore, the response to an ineffective dose of morphine (5mg/kg, i.p.) in the EPM was significantly increased in the animals that had previously received nicotine for 3 days (0.1, 0.3, 0.5 and 0.7 μg/mouse; intra-VH), 5 min prior to the injections of morphine (5mg/kg/day × 3 days; i.p.). On the other hand, the increase of morphine-induced anxiolytic-like effect in animals that had previously received the 3-day morphine (20mg/kg) was dose dependently suppressed by once daily injections of mecamylamine (0.5, 1 and 2 μg/mouse/day × 3 days; intra-VH). It is important to note that repeated intra-VH administrations of the same doses of nicotine or mecamylamine alone caused no significant change in morphine (5mg/kg)-induced anxiety-like parameters in the EPM. In conclusion, it seems that morphine sensitization affects the anxiety-like behavior in the EPM and the cholinergic system in the ventral hippocampus, via nicotinic receptors, may play an important role in this effect.

Chronic stress elevates telomerase activity in rats

The enzyme telomerase lengthens telomeres-protective structures containing repetitive DNA sequences at chromosome ends. Telomere shortening is associated with diseases of ageing in mammals. Chronic stress has been related to shorter immune-cell telomeres, but telomerase activity under stress may be low, permitting telomere loss, or high, partially attenuating it. We developed an experimental model to examine the impacts of extended unpredictable stress on telomerase activity in male rats. Telomerase activity was 54 per cent higher in stressed rats than in controls, and associated with stress-related physiological and behavioural outcomes. This significant increase suggests a potential mechanism for resilience to stress-related replicative senescence.

Exercise offers anxiolytic potential: a role for stress and brain noradrenergic-galaninergic mechanisms

Although physical activity reduces anxiety in humans, the neural basis for this response is unclear. Rodent models are essential to understand the mechanisms that underlie the benefits of exercise. However, it is controversial whether exercise exerts anxiolytic-like potential in rodents. Evidence is reviewed to evaluate the effects of wheel running, an experimental mode of exercise in rodents, on behavior in tests of anxiety and on norepinephrine and galanin systems in neural circuits that regulate stress. Stress is proposed to account for mixed behavioral findings in this literature. Indeed, running promotes an adaptive response to stress and alters anxiety-like behaviors in a manner dependent on stress. Running amplifies galanin expression in noradrenergic locus coeruleus (LC) and suppresses stress-induced activity of the LC and norepinephrine output in LC-target regions. Thus, enhanced galanin-mediated suppression of brain norepinephrine in runners is supported by current literature as a mechanism that may contribute to the stress-protective effects of exercise. These data support the use of rodents to study the emotional and neurobiological consequences of exercise.

The aqueous crude extract of Montanoa frutescens produces anxiolytic-like effects similarly to diazepam in Wistar rats: involvement of GABAA receptor

ETHNOPHARMACOLOGICAL RELEVANCE

Cihuapatli is the Nahuatl name assigned to some medicinal plants grouped in the genus Montanoa, where Montanoa frutescens (Family: Asteraceae, Tribe: Heliantheae) is included. The crude extract from these plants has been used for centuries in the Mexican traditional medicine as a remedy for reproductive impairments and mood disorders. Experimental studies have systematically corroborated the traditional use of cihuapatli on reproductive impairments and sexual motivation, however, the effect on mood and "nervous" disorders, remains to be explored.

MATERIALS AND METHODS

The anxiolytic-like effect of aqueous crude extract of M. frutescens (25, 50 and 75 mg/kg) was investigated in male Wistar rats evaluated in the elevated plus-maze and compared with several doses of diazepam (1, 2 and 4 mg/kg) as a reference anxiolytic drug. Picrotoxin (1 mg/kg), a noncompetitive antagonist of the GABA(A) receptor, was used in experimental procedures to evaluate if this receptor could be involved in the anxiolytic-like effects produced by M. frutescens. To discard hypoactivity, hyperactivity, or no changes associated with treatments, which could interfere with the behavioral activity in the elevated plus-maze, rats were subjected to the open field test.

RESULTS

M. frutescens at 50 mg/kg showed anxiolytic-like activity similarly to 2 mg/kg of diazepam, without disrupts in general motor activity. The anxiolytic-like effect of M. frutescens detected in the elevated plus-maze was blocked by picrotoxin, indicating that GABA(A) receptors are involved in the modulation of this effect.

CONCLUSIONS

The results corroborate the use of M. frutescens in folk Mexican ethnomedicine as a potential anxiolytic agent and suggest that this effect is mediated by the GABA(A) receptors. Additionally, some sedative effects with high doses of M. frutescens were detected in the present study.

The interaction of disrupted type II neuregulin 1 and chronic adolescent stress on adult anxiety- and fear-related behaviors

The incidence of anxiety, mood, substance abuse disorders and schizophrenia increases during adolescence. Epidemiological evidence confirms that exposure to stress during sensitive periods of development can create vulnerabilities that put genetically predisposed individuals at increased risk for psychiatric disorders. Neuregulin 1 (NRG1) is a frequently identified schizophrenia susceptibility gene that has also been associated with the psychotic features of bipolar disorder. Previously, we established that Type II NRG1 is expressed in the hypothalamic-pituitary-adrenal (HPA) axis neurocircuitry. We also found, using a line of Nrg1 hypomorphic rats (Nrg1(Tn)), that genetic disruption of Type II NRG1 results in altered HPA axis function and environmental reactivity. The present studies used the Nrg1(Tn) rats to test whether Type II NRG1 gene disruption and chronic stress exposure during adolescence interact to alter adult anxiety- and fear-related behaviors. Male and female Nrg1(Tn) and wild-type rats were exposed to chronic variable stress (CVS) during mid-adolescence and then tested for anxiety-like behavior, cued fear conditioning and basal corticosterone secretion in adulthood. The disruption of Type II NRG1 alone significantly impacts rat anxiety-related behavior by reversing normal sex-related differences and impairs the ability to acquire cued fear conditioning. Sex-specific interactions between genotype and adolescent stress also were identified such that CVS-treated wild-type females exhibited a slight reduction in anxiety-like behavior and basal corticosterone, while CVS-treated Nrg1(Tn) females exhibited a significant increase in cued fear extinction. These studies confirm the importance of Type II NRG1 in anxiety and fear behaviors and point to adolescence as a time when stressful experiences can shape adult behavior and HPA axis function.

Estrous cycle variations in GABA(A) receptor phosphorylation enable rapid modulation by anabolic androgenic steroids in the medial preoptic area

Anabolic androgenic steroids (AAS), synthetic testosterone derivatives that are used for ergogenic purposes, alter neurotransmission and behaviors mediated by GABA(A) receptors. Some of these effects may reflect direct and rapid action of these synthetic steroids at the receptor. The ability of other natural allosteric steroid modulators to alter GABA(A) receptor-mediated currents is dependent upon the phosphorylation state of the receptor complex. Here we show that phosphorylation of the GABA(A) receptor complex immunoprecipitated by β(2)/β(3) subunit-specific antibodies from the medial preoptic area (mPOA) of the mouse varies across the estrous cycle; with levels being significantly lower in estrus. Acute exposure to the AAS, 17α-methyltestosterone (17α-MeT), had no effect on the amplitude or kinetics of inhibitory postsynaptic currents in the mPOA of estrous mice when phosphorylation was low, but increased the amplitude of these currents from mice in diestrus, when it was high. Inclusion of the protein kinase C (PKC) inhibitor, calphostin, in the recording pipette eliminated the ability of 17α-MeT to enhance currents from diestrous animals, suggesting that PKC-receptor phosphorylation is critical for the allosteric modulation elicited by AAS during this phase. In addition, a single injection of 17α-MeT was found to impair an mPOA-mediated behavior (nest building) in diestrus, but not in estrus. PKC is known to target specific serine residues in the β(3) subunit of the GABA(A) receptor. Although phosphorylation of these β(3) serine residues showed a similar profile across the cycle, as did phosphoserine in mPOA lysates immunoprecipitated with β2/β3 antibody (lower in estrus than in diestrus or proestrus), the differences were not significant. These data suggest that the phosphorylation state of the receptor complex regulates both the ability of AAS to modulate receptor function in the mPOA and the expression of a simple mPOA-dependent behavior through a PKC-dependent mechanism that involves the β(3) subunit and other sites within the GABA(A) receptor complex.

Maternal separation enhances object location memory and prevents exercise-induced MAPK/ERK signalling in adult Sprague-Dawley rats

Early life stress increases the risk of developing psychopathology accompanied by reduced cognitive function in later life. Maternal separation induces anxiety-like behaviours and is associated with impaired memory. On the other hand, exercise has been shown to diminish anxiety-like behaviours and improve cognitive function. The effects of maternal separation and exercise on anxiety, memory and hippocampal proteins were investigated in male Sprague-Dawley rats. Maternal separation produced anxiety-like behaviours which were reversed by exercise. Maternal separation also enhanced object location memory which was not affected by exercise. Exercise did, however, increase synaptophysin and phospho-extracellular signal-regulated kinase (p-ERK) in the hippocampus of non-separated rats and this effect was not observed in maternally separated rats. These findings show that maternal separation selectively enhanced n memory and prevented activation of the MAPK/ERK signalling pathway in the adult rat hippocampus.

Quercetin protects against chronic aluminum-induced oxidative stress and ensuing biochemical, cholinergic, and neurobehavioral impairments in rats

In this study, we investigated the protective effect of chronic quercetin (a natural flavanoid) administration against Al-induced cognitive impairments, oxidative damage, and cholinergic dysfunction in male Wistar rats. Al lactate (10 mg/kg b.wt./day) was administered intragastrically to rats which were pre-treated with quercetin (10 mg/kg b.wt./day, intragastrically) for 12 weeks. At the end of 6 or 12 weeks of the study, several behavioral parameters were carried out to evaluate cognitive functions. Further after 12 weeks of exposure, various biochemical tests and H&E staining were performed to assess the extent of oxidative damage and neurodegeneration, respectively. Al levels were also estimated in HC and CS regions of rat brain. Chronic administration of quercetin caused significant improvement in the muscle coordination, cognition, anxiety, locomotion, and initial exploratory patterns in Al-treated rats. Quercetin supplementation to Al-treated animals also reduced oxidative stress, decreased ROS production, increased MnSOD activity and glutathione levels with decreased lipid peroxidation and protein oxidation. It increased AChE activity and ATP levels in HC and CS regions of rat brain compared to Al-treated rats. Quercetin administration ameliorates Al-induced neurodegenerative changes in Al-treated rats as seen by H&E staining. Further with the help of atomic absorption spectrophotometer, we found that quercetin supplementation to Al-treated rats also decreases the accumulation of Al in the HC and CS regions of rat brain. Taken together the results of this study show that quercetin offers neuroprotection against Al-induced cognitive impairments, cholinergic dysfunction, and associated oxidative damage in rats.

The effect of injury severity on behavior: a phenotypic study of cognitive and emotional deficits after mild, moderate, and severe controlled cortical impact injury in mice

Traumatic brain injury (TBI) can cause a broad array of behavioral problems including cognitive and emotional deficits. Human studies comparing neurobehavioral outcomes after TBI suggest that cognitive impairments increase with injury severity, but emotional problems such as anxiety and depression do not. To determine whether cognitive and emotional impairments increase as a function of injury severity we exposed mice to sham, mild, moderate, or severe controlled cortical impact (CCI) and evaluated performance on a variety of neurobehavioral tests in the same animals before assessing lesion volume as a histological measure of injury severity. Increasing cortical impact depth successfully produced lesions of increasing severity in our model. We found that cognitive impairments in the Morris water maze increased with injury severity, as did the degree of contralateral torso flexion, a measure of unilateral striatal damage. TBI also caused deficits in emotional behavior as quantified in the forced swim test, elevated-plus maze, and prepulse inhibition of acoustic startle, but these deficits were not dependent on injury severity. Stepwise regression analyses revealed that Morris water maze performance and torso flexion predicted the majority of the variability in lesion volume. In summary, we find that cognitive deficits increase in relation to injury severity, but emotional deficits do not. Our data suggest that the threshold for emotional changes after experimental TBI is low, with no variation in behavioral deficits seen between mild and severe brain injury.

The role of parasites and pathogens in influencing generalised anxiety and predation-related fear in the mammalian central nervous system

Behavioural and neurophysiological traits and responses associated with anxiety and predation-related fear have been well documented in rodent models. Certain parasites and pathogens which rely on predation for transmission appear able to manipulate these, often innate, traits to increase the likelihood of their life-cycle being completed. This can occur through a range of mechanisms, such as alteration of hormonal and neurotransmitter communication and/or direct interference with the neurons and brain regions that mediate behavioural expression. Whilst some post-infection behavioural changes may reflect 'general sickness' or a pathological by-product of infection, others may have a specific adaptive advantage to the parasite and be indicative of active manipulation of host behaviour. Here we review the key mechanisms by which anxiety and predation-related fears are controlled in mammals, before exploring evidence for how some infectious agents may manipulate these mechanisms. The protozoan Toxoplasma gondii, the causative agent of toxoplasmosis, is focused on as a prime example. Selective pressures appear to have allowed this parasite to evolve strategies to alter the behaviour in its natural intermediate rodent host. Latent infection has also been associated with a range of altered behavioural profiles, from subtle to severe, in other secondary host species including humans. In addition to enhancing our knowledge of the evolution of parasite manipulation in general, to further our understanding of how and when these potential changes to human host behaviour occur, and how we may prevent or manage them, it is imperative to elucidate the associated mechanisms involved.

Modeling an autism risk factor in mice leads to permanent immune dysregulation

Increasing evidence highlights a role for the immune system in the pathogenesis of autism spectrum disorder (ASD), as immune dysregulation is observed in the brain, periphery, and gastrointestinal tract of ASD individuals. Furthermore, maternal infection (maternal immune activation, MIA) is a risk factor for ASD. Modeling this risk factor in mice yields offspring with the cardinal behavioral and neuropathological symptoms of human ASD. In this study, we find that offspring of immune-activated mothers display altered immune profiles and function, characterized by a systemic deficit in CD4(+) TCRβ(+) Foxp3(+) CD25(+) T regulatory cells, increased IL-6 and IL-17 production by CD4(+) T cells, and elevated levels of peripheral Gr-1(+) cells. In addition, hematopoietic stem cells from MIA offspring exhibit altered myeloid lineage potential and differentiation. Interestingly, repopulating irradiated control mice with bone marrow derived from MIA offspring does not confer MIA-related immunological deficits, implicating the peripheral environmental context in long-term programming of immune dysfunction. Furthermore, behaviorally abnormal MIA offspring that have been irradiated and transplanted with immunologically normal bone marrow from either MIA or control offspring no longer exhibit deficits in stereotyped/repetitive and anxiety-like behaviors, suggesting that immune abnormalities in MIA offspring can contribute to ASD-related behaviors. These studies support a link between cellular immune dysregulation and ASD-related behavioral deficits in a mouse model of an autism risk factor.