Behavioral Endpoints Research Articles

Mimicking natural systems: Changes in behavior as a result of dynamic exposure to naproxen

Animals living in aquatic habitats regularly encounter anthropogenic chemical pollution. Typically, the toxicity of a chemical toxicant is determined by the median lethal concentration (LC50) through a static exposure test. However, LC50 values and static tests do not provide an accurate representation of exposure to pollutants within natural stream systems. In their native habitats, animals experience exposure as a fluctuating concentration due to turbulent mixing, temporal variations of contamination (seasonal inputs), and contaminant input type (point vs. non-point). Research has shown that turbulent environments produce exposures with a high degree of fluctuation in frequency, duration, and intensity. In order to more effectively evaluate the effects of pollutants, we created a dynamic exposure paradigm, utilizing both flow and substrate within a small mesocosm. A commonly used pharmaceutical, naproxen, was used as the toxicant and female crayfish (Orconectes virilis) as the target organism to investigate changes in fighting behavior as a result of dynamic exposure. Crayfish underwent either a 23h long static or a dynamic exposure to naproxen. Following exposure, the target crayfish and an unexposed size matched opponent underwent a 15min fight trial. These fight trials were recorded and later analyzed using a standard ethogram. Results indicate that exposure to sublethal concentrations of naproxen, in both static and flowing conditions, negatively impact aggressive behavior. Results also indicate that a dynamic exposure paradigm has a greater negative impact on behavior than a static exposure. Turbulence and habitat structure play important roles in shaping chemical exposure. Future research should incorporate features of dynamic chemical exposure in order to form a more comprehensive image of chemical exposure and predict the resulting sublethal effects from exposure. Possible techniques for assessment include utilizing flow-through experimental set-ups in tandem with behavioral or physiological endpoints as opposed to acute toxicity. Other possibilities of assessment could involve utilizing fine-scale chemical measurements of pollutants to determine the actual concentrations animals encounter during an exposure event.

Protease induced plasticity: matrix metalloproteinase-1 promotes neurostructural changes through activation of protease activated receptor 1.

Matrix metalloproteinases (MMPs) are a family of secreted endopeptidases expressed by neurons and glia. Regulated MMP activity contributes to physiological synaptic plasticity, while dysregulated activity can stimulate injury. Disentangling the role individual MMPs play in synaptic plasticity is difficult due to overlapping structure and function as well as cell-type specific expression. Here, we develop a novel system to investigate the selective overexpression of a single MMP driven by GFAP expressing cells in vivo. We show that MMP-1 induces cellular and behavioral phenotypes consistent with enhanced signaling through the G-protein coupled protease activated receptor 1 (PAR1). Application of exogenous MMP-1, in vitro, stimulates PAR1 dependent increases in intracellular Ca2+ concentration and dendritic arborization. Overexpression of MMP-1, in vivo, increases dendritic complexity and induces biochemical and behavioral endpoints consistent with increased GPCR signaling. These data are exciting because we demonstrate that an astrocyte-derived protease can influence neuronal plasticity through an extracellular matrix independent mechanism.

Unveiling the neurotoxicity of methylmercury in fish (Diplodus sargus) through a regional morphometric analysis of brain and swimming behavior assessment

The current study aims to shed light on the neurotoxicity of MeHg in fish (white seabream – Diplodus sargus) by the combined assessment of: (i) MeHg toxicokinetics in the brain, (ii) brain morphometry (volume and number of neurons plus glial cells in specific brain regions) and (iii) fish swimming behavior (endpoints associated with the motor performance and the fear/anxiety-like status). Fish were surveyed for all the components after 7 (E7) and 14 (E14) days of dietary exposure to MeHg (8.7μgg−1), as well as after a post-exposure period of 28days (PE28). MeHg was accumulated in the brain of D. sargus after a short time (E7) and reached a maximum at the end of the exposure period (E14), suggesting an efficient transport of this toxicant into fish brain. Divalent inorganic Hg was also detected in fish brain along the experiment (indicating demethylation reactions), although levels were 100–200 times lower than MeHg, which pinpoints the organic counterpart as the great liable for the recorded effects. In this regard, a decreased number of cells in medial pallium and optic tectum, as well as an increased hypothalamic volume, occurred at E7. Such morphometric alterations were followed by an impairment of fish motor condition as evidenced by a decrease in the total swimming time, while the fear/anxiety-like status was not altered. Moreover, at E14 fish swam a greater distance, although no morphometric alterations were found in any of the brain areas, probably due to compensatory mechanisms. Additionally, although MeHg decreased almost two-fold in the brain during post-exposure, the levels were still high and led to a loss of cells in the optic tectum at PE28. This is an interesting result that highlights the optic tectum as particularly vulnerable to MeHg exposure in fish. Despite the morphometric alterations reported in the optic tectum at PE28, no significant changes were found in fish behavior. Globally, the effects of MeHg followed a multiphasic profile, where homeostatic mechanisms prevented circumstantially morphometric alterations in the brain and behavioral shifts. Although it has become clear the complexity of matching brain morphometric changes and behavioral shifts, motor-related alterations induced by MeHg seem to depend on a combination of disruptions in different brain regions.

The NIH Toolbox Cognitive Battery for intellectual disabilities: three preliminary studies and future directions.

BackgroundRecent advances in understanding molecular and synaptic mechanisms of intellectual disabilities (ID) in fragile X syndrome (FXS) and Down syndrome (DS) through animal models have led to targeted controlled trials with pharmacological agents designed to normalize these underlying mechanisms and improve clinical outcomes. However, several human clinical trials have failed to demonstrate efficacy of these targeted treatments to improve surrogate behavioral endpoints. Because the ultimate index of disease modification in these disorders is amelioration of ID, the validation of cognitive measures for tracking treatment response is essential. Here, we present preliminary research to validate the National Institutes of Health Toolbox Cognitive Battery (NIH-TCB) for ID.MethodsWe completed three pilot studies of patients with FXS (total n = 63; mean age 19.3 ± 8.3 years, mean mental age 5.3 ± 1.6 years), DS (n = 47; mean age 16.1 ± 6.2, mean mental age 5.4 ± 2.0), and idiopathic ID (IID; n = 16; mean age 16.1 ± 5.0, mean mental age 6.6 ± 2.3) measuring processing speed, executive function, episodic memory, word/letter reading, receptive vocabulary, and working memory using the web-based NIH-TB-CB, addressing feasibility, test-retest reliability, construct validity, ecological validity, and syndrome differences and profiles.ResultsFeasibility was good to excellent (≥80 % of participants with valid scores) for above mental age 4 years for all tests except list sorting (working memory). Test-retest stability was good to excellent, and convergent validity was similar to or better than results obtained from typically developing children in the normal sample for executive function and language measures. Examination of ecological validity revealed moderate to very strong correlations between the NIH-TCB composite and adaptive behavior and full-scale IQ measures. Syndrome/group comparisons demonstrated significant deficits for the FXS and DS groups relative to IID on attention and inhibitory control, a significant reading weakness for FXS, and a receptive vocabulary weakness for DS.ConclusionsThe NIH-TCB has potential for assessing important dimensions of cognition in persons with ID, and several tests may be useful for tracking response to intervention. However, more extensive psychometric studies, evaluation of the NIH-TCB’s sensitivity to change, both developmentally and in the context of treatment, and perhaps establishing links to brain function in these populations, are required to determine the true utility of the battery as a set of outcome measures.

Meta-Analysis and Systematic Review of Neural Stem Cells therapy for experimental ischemia stroke in preclinical studies.

To evaluate the preclinical studies using NSCs transplantation therapy for experimental ischemic stroke, and determine the effect size of NSCs therapy and the correlations between different clinical measures. We firstly searched literatures to identify studies of NSCs therapy in animal cerebral ischemia models, and then calculated the quality score of studies, assessed the effect size of NSCs therapy relative to behavioral and histologic endpoints by meta-analysis. A total of 37 studies and 54 independent treated interventions were used for systematic review and meta-analysis. The median quality score was 5 of 10. 36 studies (53 intervention arms) reported functional outcome, 22 studies (34 intervention arms) reported structural outcome. After adjusted by subgroup and sensitivity analysis, the mean effect sizes were improved by 1.35 for mNSS, 1.84 for rotarod test, 0.61 for cylinder test, and 0.84 for infarct volume. Furthermore, effect size had a certain interaction with clinical variables, for example early NSCs therapy etc. In this preclinical studies, we demonstrated that transplanted NSCs significantly improved outcomes (both functional and structural outcome) in ischemic stroke. It is suggested that future preclinical animal model studies of stroke should improve study quality validity and reduce potentially confounded publication bias.

Comparative Developmental Toxicity of Flavonoids Using an Integrative Zebrafish System.

Flavonoids are a large, structurally diverse class of bioactive naturally occurring chemicals commonly detected in breast milk, soy based infant formulas, amniotic fluid, and fetal cord blood. The potential for pervasive early life stage exposures raises concerns for perturbation of embryogenesis, though developmental toxicity and bioactivity information is limited for many flavonoids. Therefore, we evaluated a suite of 24 flavonoid and flavonoid-like chemicals using a zebrafish embryo-larval toxicity bioassay-an alternative model for investigating developmental toxicity of environmentally relevant chemicals. Embryos were exposed to 1-50 µM of each chemical from 6 to 120 h postfertilization (hpf), and assessed for 26 adverse developmental endpoints at 24, 72, and 120 hpf. Behavioral changes were evaluated in morphologically normal animals at 24 and 72 hpf, at 120 hpf using a larval photomotor response (LPR) assay. Gene expression was comparatively evaluated for all compounds for effects on biomarker transcripts indicative of AHR (cyp1a) and ER (cyp19a1b, esr1, lhb, vtg) pathway bioactivity. Overall, 15 of 24 flavonoids elicited adverse effects on one or more of the developmental or behavioral endpoints. Hierarchical clustering and principle component analyses compared toxicity profiles and identified 3 distinct groups of bioactive flavonoids. Despite robust induction of multiple estrogen-responsive biomarkers, co-exposure with ER and GPER antagonists did not ameliorate toxicity, suggesting ER-independence and alternative modes of action. Taken together, these studies demonstrate that development is sensitive to perturbation by bioactive flavonoids in zebrafish that are not related to traditional estrogen receptor mode of action pathways. This integrative zebrafish platform provides a useful framework for evaluating flavonoid developmental toxicity and hazard prioritization.

Zebrafish Models to Study Fear and Anxiety

Background: Psychiatric disorders related to fear and anxiety are common throughout the world, and their neurobiological mechanisms are not fully understood. Studying animal models has been a common strategy to probe mechanisms of normal and pathological brain functioning. Experimental paradigms originally developed with mammalian models, such as predator exposure, fear learning, exposure to predator-related olfactory cues and novelty, have been aquatically tailored for a newer model in translational neuroscience, the zebrafish. Objective: Our aim was to explore the utility of zebrafish models of fear and anxiety and to describe currently employed experimental paradigms, as well as relevant behavioral endpoints and biomarkers. Conclusion: We conclude that zebrafish are a promising model to help elucidate the underlying mechanisms related to fear and anxiety. This is partly due to robust behavioral and endocrine responses, pharmacological sensitivity, ease of genetic manipulation, and amenability to high-throughput screening due to low-cost and small size. However, the zebrafish is a relatively new model and further research is needed to truly exploit the potential of this aquatic species. Keywords: Zebrafish, fear, anxiety, predator, novelty, cortisol, biomarkers.

Fine sediment as environmental stressor affecting freshwater mussel behavior and ecosystem services

Fine sediment pollution is considered a major stressor for aquatic ecosystems and their biodiversity. In particular, fine sediments have been suggested to play a crucial role in the declines of freshwater mussels which are considered keystone fauna of streams and rivers. Whereas the effects of deposited fine sediments on recruitment failure are well known, effects of suspended fine sediments on adult mussel behavior are less studied. Therefore the aim of this study was to investigate the effects of fine sediment exposure on freshwater mussel behavior and on mussel-dependent ecosystem services. Unio pictorum mussels were used to test three behavioral endpoints: Hall activity, transition frequency and relative water clearance rate. Mussels were exposed to fine sediments of different particle size classes (<45μm, 45–63μm, 63–125μm) and different concentration (0–10gL−1) of the smallest particle size class. Hall sensor technology and turbidity measurements were used to detect mussel behavior in presence of suspended sediments. Results revealed that mussels improve clearance of suspended particles out of the water column by 35%, independent of particle size class and concentration. Transition frequency was determined an unsuitable behavioral endpoint for non-soluble substances. Contrary to previous studies, we could demonstrate that fine sediments do not interfere with filtration by mussels and that mussels have a great influence on water purification, providing a valuable ecosystem service.

A novel method for automated tracking and quantification of adult zebrafish behaviour during anxiety

BackgroundBehavioural neuroscience relies on software driven methods for behavioural assessment, but the field lacks cost-effective, robust, open source software for behavioural analysis. New MethodHere we propose a novel method which we called as ZebraTrack. It includes cost-effective imaging setup for distraction-free behavioural acquisition, automated tracking using open-source ImageJ software and workflow for extraction of behavioural endpoints. Our ImageJ algorithm is capable of providing control to users at key steps while maintaining automation in tracking without the need for the installation of external plugins. ResultsWe have validated this method by testing novelty induced anxiety behaviour in adult zebrafish. Our results, in agreement with established findings, showed that during state-anxiety, zebrafish showed reduced distance travelled, increased thigmotaxis and freezing events. Furthermore, we proposed a method to represent both spatial and temporal distribution of choice-based behaviour which is currently not possible to represent using simple videograms. Comparison with existing method(s)ZebraTrack method is simple and economical, yet robust enough to give results comparable with those obtained from costly proprietary software like Ethovision XT. ConclusionWe have developed and validated a novel cost-effective method for behavioural analysis of adult zebrafish using open-source ImageJ software.

Benzodiazepine and neuroactive steroid combinations in rats: anxiolytic-like and discriminative stimulus effects.

Benzodiazepines are effective anxiolytics, hypnotics, and anticonvulsants but unwanted side effects, including abuse potential, limit their use. A possible strategy to increase the therapeutic index of this drug class is to combine benzodiazepines with neuroactive steroids. The present study evaluated the extent to which combinations of benzodiazepines (triazolam, clonazepam) and neuroactive steroids (pregnanolone, ganaxolone) induced additive, supra-additive, or infra-additive effects in an elevated zero maze and a drug discrimination procedure in rats. Male Sprague-Dawley rats (N = 7/group) were placed into an elevated zero maze apparatus following injections of multiple doses of triazolam and pregnanolone, alone and combined, or clonazepam and ganaxolone, alone and combined. These drugs/drug combinations also were evaluated in rats (N = 8) trained to discriminate triazolam (0.1mg/kg, i.p.) from vehicle. Drug interactions were evaluated using isobolographic and dose-addition analysis. In the elevated zero maze, all drugs engendered dose-dependent increases in time spent in the open quadrant when administered alone. Triazolam and pregnanolone, as well as clonazepam and ganaxolone combinations produced additive or supra-additive effects depending on the fixed-proportion that was tested. In triazolam discrimination, all drugs engendered dose-dependent increases in triazolam-lever responding. In combination, triazolam and pregnanolone and clonazepam and ganaxolone produced predominantly additive discriminative stimulus effects, except for one fixed proportion of clonazepam and ganaxolone which had supra-additive effects. Although drug interactions depended on the constituent drugs, the combination tested, and the behavioral endpoint; a combination was identified that would be predicted to result in supra-additive anxiolytic-like effects with predominantly additive discriminative stimulus effects.

Acetaminophen use in pregnancy and neurodevelopment: attention function and autism spectrum symptoms.

Acetaminophen is extensively used during pregnancy. But there is a lack of population-representative cohort studies evaluating its effects on a range of neuropsychological and behavioural endpoints. We aimed to assess whether prenatal exposure to acetaminophen is adversely associated with neurodevelopmental outcomes at 1 and 5 years of age. This Spanish birth cohort study included 2644 mother-child pairs recruited during pregnancy. The proportion of liveborn participants evaluated at 1 and 5 years was 88.8% and 79.9%, respectively. Use of acetaminophen was evaluated prospectively in two structured interviews. Ever/never use and frequency of use (never, sporadic, persistent) were measured. Main neurodevelopment outcomes were assessed using Childhood Autism Spectrum Test (CAST), Conner's Kiddie Continuous Performance Test (K-CPT) and ADHD-DSM-IV form list. Regression models were adjusted for social determinants and co-morbidities. Over 40% of mothers reported using acetaminophen. Ever-exposed offspring had higher risks of presenting more hyperactivity/impulsivity symptoms [incidence rate ratio (IRR) = 1.41, 95% confidence interval (CI) 1.01-1.98), K-CPT commission errors (IRR = 1.10, 1.03-1.17), and lower detectability scores (coefficient β = -0.75, -0.13--0.02). CAST scores were increased in ever-exposed males (β = 0.63, 0.09-1.18). Increased effect sizes of risks by frequency of use were observed for hyperactivity/impulsivity symptoms (IRR = 2.01, 0.95-4.24) in all children, K-CPT commission errors (IRR = 1.32, 1.05-1.66) and detectability (β = -0.18, -0.36-0.00) in females, and CAST scores in males (β = 1.91, 0.44-3.38). Prenatal acetaminophen exposure was associated with a greater number of autism spectrum symptoms in males and showed adverse effects on attention-related outcomes for both genders. These associations seem to be dependent on the frequency of exposure.

Neuroinflammation and Behavior in HIV-1 Transgenic Rats Exposed to Chronic Adolescent Stress.

Highly active antiretroviral therapy (HAART) has improved prognosis for people living with HIV (PLWH) and dramatically reduced the incidence of AIDS. However, even when viral load is controlled, PLWH develop psychiatric and neurological disorders more frequently than those living without HIV. Adolescents with HIV are particularly susceptible to the development of psychiatric illnesses and neurocognitive impairments. While both psychiatric and neurocognitive disorders have been found to be exacerbated by stress, the extent to which chronic stress and HIV-1 viral proteins interact to impact behavior and relevant neuroinflammatory processes is unknown. Determination of the individual contributions of stress and HIV to neuropsychiatric disorders is heavily confounded in humans. In order to isolate the influence of HIV-1 proteins and chronic stress on behavior and neuroinflammation, we employed the HIV-1 transgenic (Tg) rat model, which expresses HIV-1 proteins with a gag and pol deletion, allowing for viral protein expression without viral replication. This Tg line has been characterized as a model of HAART-controlled HIV-1 infection due to the lack of viral replication but continued presence of HIV-1 proteins. We exposed male and female adolescent HIV-1 Tg rats to a mixed-modality chronic stress paradigm consisting of isolation, social defeat and restraint, and assessed behavior, cerebral vascularization, and neuroinflammatory endpoints. Stress, sex, and presence of the HIV-1 transgene impacted weight gain in adolescent rats. Female HIV-1 Tg rats showed decreases in central tendency during the light cycle in the open field regardless of stress exposure. Both male and female HIV-1 Tg rats exhibited decreased investigative behavior in the novel object recognition task, but no memory impairments. Adolescent stress had no effect on the tested behaviors. Microglia in female HIV-1 Tg rats exhibited a hyper-ramified structure, and gene expression of complement factor B was increased in the hippocampus. In addition, adolescent stress exposure increased microglial branching and junctions in female wild-type rats without causing any additional increase in HIV-1 rats. These data suggest that the presence of HIV-1 proteins during development leads to alterations in behavioral and neuroinflammatory endpoints that are not further impacted by concurrent chronic adolescent stress.

Granulocyte-colony stimulating factor promotes brain repair following traumatic brain injury by recruitment of microglia and increasing neurotrophic factor expression.

The overall objective was to elucidate cellular mechanisms by which G-CSF enhances recovery from traumatic brain injury in a hippocampal-dependent learning task. Chimeric mice were prepared by transplanting bone marrow cells that express green fluorescent protein (GFP+) from a transgenic "green" mice into C57BL/6 mice. Two months later, the animals sustained mild controlled cortical impact (CCI) to the right frontal-parietal cortex, followed by G-CSF (100 μg/kg) treatment for 3 consecutive days. The primary behavioral end-point was performance on the radial arm water maze (RAWM) assessed before and after CCI (days 7 and 14). Secondary endpoints included a), motor performance on a rotating cylinder (rotarod), b) measurement of microglial and astroglial response, c) hippocampal neurogenesis, and d) measures of neurotrophic factors (BDNF, GDNF) in brain homogenates. G-CSF treatment resulted in significantly better performance on the rotorod at one week, and in the RAWM after one and two weeks. The cellular changes found 2 wks after CCI in the G-CSF group included increased numbers of hippocampal newborn neurons as well as astrocytosis and microgliosis in striatum and frontal cortex on both sides of brain. GFP+ cells that co-labeled with Iba1 (microglial marker) comprised a significant proportion of striatal microglia in G-CSF treated animals, indicating the capacity of G-CSF to increase microglial recruitment to the site of injury. Neurotrophic factors GDNF and BDNF, elaborated by activated microglia and astrocytes, were increased in G-CSF treated mice. G-CSF serves as a neurotrophic factor that increases hippocampal neurogenesis (or enhances survival of new-born neurons), and activates astrocytes and microglia. In turn, these activated glia release a plethora of cytokines and neurotrophic factors that contribute, in a poorly understood cascade, to the brain's repair response. G-CSF also acts directly on bone marrow-derived cells to enhance recruitment of microglia to the site of CCI from circulating monocytes to the site of CCI.

Adverse effects of the SSRI antidepressant sertraline on early life stages of marine invertebrates

Widespread contamination of coastal environments by emerging compounds includes low concentrations of pharmaceuticals. These pollutants are not currently incorporated in monitoring programs despite their effects on non-target organisms are very little documented. Among the selective serotonin reuptake inhibitor (SSRI) antidepressants, sertraline (SRT) is one of the most prescribed globally. In this work, earlier life stages of Amphibalanus amphitrite, Brachionus plicatilis and Mytilus galloprovincialis were exposed to environmental concentrations of SRT in order to study both sub-lethal and lethal responses in 24/48 h-tests. Low concentrations of SRT altered significantly swimming behavior in A. amphitrite and B. plicatilis giving 48 h-EC50 (μg/L) of 113.88 and 282.23, respectively whereas higher values were observed for mortality and immobilization. EC50 embryotoxicity with M. galloprovincialis was 206.80 μg/L. This work add new data about SRT ecotoxicity on marine invertebrates and confirms the applicability of behavioral endpoints to evaluate the environmental impact of antidepressants in marine organisms.

Behavioral assessment of neuropathic pain, fatigue, and anxiety in experimental autoimmune encephalomyelitis (EAE) and attenuation by interleukin-10 gene therapy

Relapsing-remitting multiple sclerosis is commonly associated with motor impairments, neuropathic pain, fatigue, mood disorders, and decreased life expectancy. However, preclinical pharmacological studies predominantly rely on clinical scoring of motor deficit as the sole behavioral endpoint. Thus, the translational potential of these studies is limited. Here, we have assessed the therapeutic potential of a novel anti-inflammatory interleukin-10 (IL-10) non-viral gene therapy formulation (XT-101-R) in a rat relapsing remitting experimental autoimmune encephalomyelitis (EAE) model. EAE induced motor deficits and neuropathic pain as reflected by induction of low-threshold mechanical allodynia, suppressed voluntary wheel running, decreased social exploration, and was associated with markedly enhanced mortality. We also noted that voluntary wheel running was depressed prior to the onset of motor deficit, and may therefore serve as a predictor of clinical symptoms onset. XT-101-R was intrathecally dosed only once at the onset of motor deficits, and attenuated each of the EAE-induced symptoms and improved survival, relative to vehicle control. This is the first pharmacological assessment of such a broad range of EAE symptoms, and provides support for IL-10 gene therapy as a clinical strategy for the treatment of multiple sclerosis.

The Rapidly Acting Antidepressant Ketamine and the mGlu2/3 Receptor Antagonist LY341495 Rapidly Engage Dopaminergic Mood Circuits.

Ketamine is a rapidly acting antidepressant in patients with treatment-resistant depression (TRD). Although the mechanisms underlying these effects are not fully established, inquiry to date has focused on the triggering of synaptogenesis transduction pathways via glutamatergic mechanisms. Preclinical data suggest that blockade of metabotropic glutamate (mGlu2/3) receptors shares many overlapping features and mechanisms with ketamine and may also provide rapid efficacy for TRD patients. Central dopamine circuitry is recognized as an end target for mood regulation and hedonic valuation and yet has been largely neglected in mechanistic studies of antidepressant-relevant effects of ketamine. Herein, we evaluated the changes in dopaminergic neurotransmission after acute administration of ketamine and the mGlu2/3 receptor antagonist LY341495 [(2S)-2-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid ] in preclinical models using electrophysiologic, neurochemical, and behavioral endpoints. When given acutely, both ketamine and LY341495, but not the selective serotonin reuptake inhibitor (SSRI) citalopram, increased the number of spontaneously active dopamine neurons in the ventral tegmental area (VTA), increased extracellular levels of dopamine in the nucleus accumbens and prefrontal cortex, and enhanced the locomotor stimulatory effects of the dopamine D2/3 receptor agonist quinpirole. Further, both ketamine and LY341495 reduced immobility time in the tail-suspension assay in CD1 mice, which are relatively resistant to SSRI antidepressants. Both the VTA neuronal activation and the antidepressant phenotype induced by ketamine and LY341495 were attenuated by the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo- (9CI)-benzo[f]quinoxaline-7-sulfonamide, indicating AMPA-dependent effects. These findings provide another overlapping mechanism of action of ketamine and mGlu2/3 receptor antagonism that differentiates them from conventional antidepressants and thus support the potential rapidly acting antidepressant actions of mGlu2/3 receptor antagonism in patients.

Comparison of Burrowing and Stimuli-Evoked Pain Behaviors as End-Points in Rat Models of Inflammatory Pain and Peripheral Neuropathic Pain.

Establishment and validation of ethologically-relevant, non-evoked behavioral end-points as surrogate measures of spontaneous pain in rodent pain models has been proposed as a means to improve preclinical to clinical research translation in the pain field. Here, we compared the utility of burrowing behavior with hypersensitivity to applied mechanical stimuli for pain assessment in rat models of chronic inflammatory and peripheral neuropathic pain. Briefly, groups of male Sprague-Dawley rats were habituated to the burrowing environment and trained over a 5-day period. Rats that burrowed ≤ 450 g of gravel on any 2 days of the individual training phase were excluded from the study. The remaining rats received either a unilateral intraplantar injection of Freund's complete adjuvant (FCA) or saline, or underwent unilateral chronic constriction injury (CCI) of the sciatic nerve- or sham-surgery. Baseline burrowing behavior and evoked pain behaviors were assessed prior to model induction, and twice-weekly until study completion on day 14. For FCA- and CCI-rats, but not the corresponding groups of sham-rats, evoked mechanical hypersensitivity developed in a temporal manner in the ipsilateral hindpaws. Although burrowing behavior also decreased in a temporal manner for both FCA-and CCI- rats, there was considerable inter-animal variability. By contrast, mechanical hyperalgesia and mechanical allodynia in the ipsilateral hindpaws of FCA- and CCI-rats respectively, exhibited minimal inter-animal variability. Our data collectively show that burrowing behavior is altered in rodent models of chronic inflammatory pain and peripheral neuropathic pain. However, large group sizes are needed to ensure studies are adequately powered due to considerable inter-animal variability.

Disruption, but not overexpression of urate oxidase alters susceptibility to pentylenetetrazole- and pilocarpine-induced seizures in mice.

There is a continuous drive to find new, improved therapies that have a different mechanism of action in order to help diminish the sizable percentage of persons with pharmacoresistant epilepsy. Uric acid is increasingly recognized as contributing to the pathophysiology of multiple disorders, and there are indications that uric acid might play a role in epileptic mechanisms. Nevertheless, studies that directly investigate its involvement are lacking. In this study we assessed the susceptibility to pentylenetetrazole- and pilocarpine-induced seizures in mice with genetically altered uric acid levels by targeting urate oxidase, which is the enzyme responsible for uric acid breakdown. We found that although disruption of urate oxidase resulted in a decreased susceptibility to all behavioral end points in both seizure models, overexpression did not result in any alterations when compared to their wild-type littermates. Our results suggest that a chronic increase in uric acid levels may result in decreased brain excitability.

Old model organisms and new behavioral end-points: Swimming alteration as an ecotoxicological response

Behavioral responses of aquatic organisms have received much less attention than developmental or reproductive ones due to the scarce presence of user-friendly tools for their acquisition. The technological development of data acquisition systems for quantifying behavior in the aquatic environment and the increase of studies on the understanding the relationship between the behavior of aquatic organisms and the physiological/ecological activities have generated renewed interest in using behavioral responses also in marine ecotoxicology. Recent reviews on freshwater environment show that behavioral end-points are comparatively fast and sensitive, and warrant further attention as tools for assessing the toxicological effects of environmental contaminants. In this mini-review, we perform a systematic analysis of the most recent works that have used marine invertebrate swimming alteration as behavioral end-point in ecotoxicological studies by assessing the differences between behavioral and acute responses in a wide range of species, in order to compare their sensitivity.

Physiological and Behavioral Effects of Exposure to Environmentally Relevant Concentrations of Prednisolone During Zebrafish (Danio rerio) Embryogenesis.

The presence of synthetic glucocorticoids within the aquatic environment has been highlighted as a potential environmental concern as they may mimic the role of endogenous glucocorticoids during vertebrate ontogeny. Prednisolone is a commonly prescribed synthetic glucocorticoid which has been repeatedly detected in the environment. This study investigated the impact of environmentally relevant concentrations of prednisolone (0.1, 1, and 10 μg/L) during zebrafish embryogenesis using physiological and behavioral end points which are known to be mediated by endogenous glucocorticoids. The frequency of spontaneous muscle contractions (24 hpf) was significantly reduced by prednisolone and 0.1 μg/L increased the distance embryos swam in response to a mechanosensory stimulus (48 hpf). The percentage of embryos hatched significantly increased following prednisolone treatment (1 and 10 μg/L), while growth and mortality were unaffected. The onset of heart contraction was differentially affected by prednisolone while heart rate and oxygen consumption both increased significantly throughout embryogenesis. No substantial effect on the axial musculature was observed. Morphological changes to the lower jaw were detected at 96 hpf in response to 1 μg/L of prednisolone. Several parameters of swim behavior were also significantly affected. Environmentally relevant concentrations of prednisolone therefore alter early zebrafish ontogeny and significantly affect embryo behavior.