Replicating human characteristics: A promising animal model of central fatigue

Central fatigue is a common pathological state characterized by psychological loss of drive, lack of appetite, drowsiness, and decreased psychic alertness. The mechanism underlying central fatigue is still unclear, and there is no widely accepted successful animal model that fully represents human characteristics. We aimed to construct a more clinically relevant and comprehensive animal model of central fatigue. In this study, we utilized the Modified Multiple Platform Method (MMPM) combined with alternate-day fasting (ADF) to create the animal model. The model group rats are placed on a stationary water environment platform for sleep deprivation at a fixed time each day, and they were subjected to ADF treatment. On non-fasting days, the rats were allowed unrestricted access to food. This process was sustained over a period of 21 days. We evaluated the model using behavioral assessments such as open field test, elevated plus maze test, tail suspension test, Morris water maze test, grip strength test, and forced swimming test, as well as serum biochemical laboratory indices. Additionally, we conducted pathological observations of the hippocampus and quadriceps muscle tissues, transmission electron microscope observation of mitochondrial ultrastructure, and assessment of mitochondrial energy metabolism and oxidative stress-related markers. The results revealed that the model rats displayed emotional anomalies resembling symptoms of depression and anxiety, decreased exploratory behavior, decline in learning and memory function, and signs of skeletal muscle fatigue, successfully replicating human features of negative emotions, cognitive decline, and physical fatigue. Pathological damage and mitochondrial ultrastructural alterations were observed in the hippocampus and quadriceps muscle tissues, accompanied by abnormal mitochondrial energy metabolism and oxidative stress in the form of decreased ATP and increased ROS levels. In conclusion, our ADF+MMPM model comprehensively replicated the features of human central fatigue and is a promising platform for preclinical research. Furthermore, the pivotal role of mitochondrial energy metabolism and oxidative stress damage in the occurrence of central fatigue in the hippocampus and skeletal muscle tissues was corroborated.

Impact of Codonopsis decoction on cerebral blood flow and cognitive function in rats with chronic cerebral ischemia

ETHNOPHARMACOLOGICAL RELEVANCE

Some species of Codonopsis (local name in Shanxi: Ludang) have long demonstrated high medicinal and economic value. Radix Codonopsis, the dried root of Codonopsis pilosula (Franch.) Nannf. (C. pilosula), Codonopsis pilosula var. modesta (Nannf.) L.D.Shen (C. pilosula var. modesta), or Codonopsis pilosula subsp. tangshen (Oliv.) D.Y.Hong (C. pilosula subsp. tangshen), was recorded as a traditional Chinese medicine back in the Qing Dynasty in Ben Cao Cong Xin. Radix Codonopsis, a valuable medicinal herb certified by the Chinese National Geographic Indication, is known for invigorating the spleen, nourishing the lungs, promoting blood circulation, and generating fluid properties. Given that chronic cerebral ischemia (CCI) is often associated with the symptoms of qi and blood deficiencies and fluid depletion, we explored the potential of Codonopsis decoction in the treatment of CCI.

STUDY AIMS

We investigated the effects of Codonopsis decoction on cerebral blood flow (CBF) and cognitive function in rats with bilateral carotid artery occlusion after surgery; explored whether Codonopsis decoction alleviates pathological injuries in brain tissue of rats after 2-VO surgery; and assessed the impact of Codonopsis decoction on the expression of chemokines, hypoxia-inducible factors, and inflammatory mediators in rats after 2-VO surgery.

MATERIALS AND METHODS

We used a 2-VO rat model to simulate CCI. We used a laser speckle imaging (LSI) system to observe changes in CBF before and after surgery. The goal was to examine variations in CBF at different time points after 2-VO surgery. For 4 weeks, the rats were orally administered Codonopsis decoction at doses of 2.7, 5.4, and 10.8 g/kg/day, or Ginaton at a dose of 43.2 mg/kg/day. To assess the effect of Codonopsis on cerebral hypoperfusion symptoms in rats, we conducted the Morris water maze (MWM), Barnes maze (BM), and forelimb grip strength tests. Additionally, pathological experiments including hematoxylin and eosin, Nissl, and Luxol fast blue staining were conducted. Furthermore, we used western blotting to detect changes in the levels of proteins such as the chemotactic factor CKLF1 and hypoxia-inducible actor 1-alpha (HIF-1α).

RESULTS

One week after 2-VO surgery, cerebral arterial blood supply in the rats rapidly reduced to approximately 43.39% ± 3.53% of the preoperative level. Cerebral cortex perfusion reached its nadir within 24 h of surgery, gradually recovering and stabilizing by the fourth week after surgery. An integration of the results from the BM, MWM, and grip strength tests, which assessed cognitive function and forelimb strength in rats after 2-VO surgery, unequivocally revealed that Codonopsis treatment significantly reduced the latency period and increased the number of platform crossings in the MWM test. Ginaton exhibited a comparable effect. Moreover, both Codonopsis and Ginaton decreased the number of errors and the time required to locate the target hole in the BM test. Histopathological staining revealed that Codonopsis and Ginaton could ameliorate pathological damage in rats after CCI and reduce the release of factors such as CKLF1 and HIF-1α.

CONCLUSION

Codonopsis decoction exerted its protective effects on CCI rats possibly by modulating the levels of chemokines, hypoxia-inducible factors, and neuroinflammatory mediators.

Rodent tests of depression and anxiety: Construct validity and translational relevance

Behavioral testing constitutes the primary method to measure the emotional states of nonhuman animals in preclinical research. Emerging as the characteristic tool of the behaviorist school of psychology, behavioral testing of animals, particularly rodents, is employed to understand the complex cognitive and affective symptoms of neuropsychiatric disorders. Following the symptom-based diagnosis model of the DSM, rodent models and tests of depression and anxiety focus on behavioral patterns that resemble the superficial symptoms of these disorders. While these practices provided researchers with a platform to screen novel antidepressant and anxiolytic drug candidates, their construct validity-involving relevant underlying mechanisms-has been questioned. In this review, we present the laboratory procedures used to assess depressive- and anxiety-like behaviors in rats and mice. These include constructs that rely on stress-triggered responses, such as behavioral despair, and those that emerge with nonaversive training, such as cognitive bias. We describe the specific behavioral tests that are used to assess these constructs and discuss the criticisms on their theoretical background. We review specific concerns about the construct validity and translational relevance of individual behavioral tests, outline the limitations of the traditional, symptom-based interpretation, and introduce novel, ethologically relevant frameworks that emphasize simple behavioral patterns. Finally, we explore behavioral monitoring and morphological analysis methods that can be integrated into behavioral testing and discuss how they can enhance the construct validity of these tests.

Coordination function index: A novel indicator for assessing hindlimb locomotor recovery in spinal cord injury rats based on catwalk gait parameters

In preclinical studies of spinal cord injury (SCI), behavioral assessments are crucial for evaluating treatment effectiveness. Commonly used methods include Basso, Beattie, Bresnahan (BBB) score and the Louisville swim scale (LSS), relying on subjective observations. The CatWalk automated gait analysis system is also widely used in SCI studies, providing extensive gait parameters from footprints. However, these parameters are often used independently or combined simply without utilizing the vast amount of data provided by CatWalk. Therefore, it is necessary to develop a novel approach encompassing multiple CatWalk parameters for a comprehensive and objective assessment of locomotor function. In this work, we screened 208 CatWalk XT gait parameters and identified 38 suitable for assessing hindlimb motor function recovery in a rat thoracic contusion SCI model. Exploratory factor analysis was used to reveal structural relationships among these parameters. Weighted scores for Coordination effectively differentiated hindlimb motor function levels, termed as the Coordinated Function Index (CFI). CFI showed high reliability, exhibiting high correlations with BBB scores, LSS, and T2WI lesion area. Finally, we simplified CFI based on factor loadings and correlation analysis, obtaining a streamlined version with reliable assessment efficacy. In conclusion, we developed a systematic assessment indicator utilizing multiple CatWalk parameters to objectively evaluate hindlimb motor function recovery in rats after thoracic contusion SCI.

A review of behavioral methods for the evaluation of cognitive performance in animal models: Current techniques and links to human cognition

INTRODUCTION

Memory is defined as the ability to store, maintain and retrieve information. Learning is the acquisition of information that changes behavior and memory. Stress, dementia, head trauma, amnesia, Alzheimer's, Huntington, Parkinson's, Wernicke-Korsakoff syndrome (WKS) may be mentioned among the diseases in which memory and learning are affected. The task of understanding deficits in memory and learning in humans is daunting due to the complexity of neural and cognitive mechanisms in the nervous system. This job is made more difficult for clinicians and researchers by the fact that many techniques used to research memory are not ethically acceptable or technically feasible for use in humans. Thus, animal models have been necessary alternative for studying normal and disordered learning and memory. This review attempts to bridge these domains to allow biomedical researchers to have a firm grasp of "memory" and "learning" as constructs in humans whereby they may then select the proper animal cognitive test.

RESULTS AND CONCLUSION

Various tests (open field habituation test, Y-maze test, passive avoidance test, step-down inhibitory avoidance test, active avoidance test, 8-arms radial maze test, Morris water maze test, radial arm water maze, novel object recognition test and gait function test) have been designed to evaluate different kinds of memory. Each of these tests has their strengths and limits. Abnormal results obtained using these tasks in non-human animals indicate malfunctions in memory which may be due to several physiological and psychological diseases of nervous system. Further studies by using the discussed tests can be very beneficial for achieving a therapeutic answer to these diseases.

Ecotoxicological responses of Eisenia andrei exposed in field-contaminated soils by sanitary sewage

The disposal of untreated sanitary sewage in the soil has several consequences for human health and leads to environmental risks; thus, it is necessary investigating, monitoring and remediating the affected sites. The aims of the current study are to evaluate ecotoxicological effects on Eisenia andrei earthworms exposed to soil subjected to sources of sanitary sewage discharge and to investigate whether prevention values established by the Brazilian legislation for soil quality, associated with the incidence of chemical substances in it, are satisfactory enough to assure the necessary quality for different organisms. Earthworms' behavior, reproduction, acetylcholinesterase activity, catalase, superoxide dismutase and malondialdehyde levels were evaluated. The reproduction and behavior of earthworms exposed to sanitary sewage were adversely affected. Increased superoxide dismutase and catalase activity acted as antioxidant defense mechanism. Significantly increased lipid peroxidation levels and acetylcholinesterase activity inhibition have indicated lipid peroxidation in cell membrane and neurotransmission changes, respectively. Results have confirmed that sanitary sewage induced oxidative stress in earthworms. In addition, based on biochemical data analysis, the integrated biomarker response (IBR) has evidenced different toxicity levels in earthworms between the investigated points. Finally, results have indicated that effluents released into the soil, without proper treatment, lead to contaminant accumulation due to soil saturation and it can hinder different processes and biological development taking place in the soil. In addition, the current study has shown that physical-chemical analyses alone are not enough to assess soil quality, since it is also requires adopting an ecotoxicological approach. Brazilian legislation focused on soil quality must be revised and new guiding values must be proposed.

Behavioral testing in animal models of spinal cord injury

This review is based on a lecture presented at the Craig H. Neilsen Foundation sponsored Spinal Cord Injury Training Program at Ohio State University. We discuss the advantages and challenges of injury models in rodents and theory relation to various behavioral outcome measures. We offer strategies and advice on experimental design, behavioral testing, and on the challenges, one will encounter with animal testing. This review is designed to guide those entering the field of spinal cord injury and/or involved with in vivo animal testing.

An active avoidance behavioral paradigm for use in a mild closed head model of traumatic brain injury in mice

BACKGROUND

A mild traumatic brain injury (TBI) occurs to millions of people each year. Translational approaches to understanding the pathogenesis of neurological diseases and the testing of the effectiveness of interventions typically require cognitive function assays in rodents.

NEW METHODS

Our goal was to validate the active avoidance task using the GEMINI avoidance system in a mouse model of mild closed head injury (CHI).

RESULTS

We found that shock intensity had only a marginal effect on the test. We found that sex was an important biological variable, as female mice learned the task better than male mice. We demonstrate that a single mild CHI in mice caused deficits in the task at four weeks post-injury.

COMPARISON WITH EXISTING METHODS

Active avoidance is a classical conditioning test in which mice must pair the presence of a conditioned stimulus with moving between two chambers to avoid an electric shock. External conditions (i.e., apparatus), as well as inherent differences in the mice, which may not be directly linked to the model of the disease (i.e., sensory differences), can affect the reproducibility of a behavioral assay. Before our study, there was a lack of standard operating procedures and validated methods for the active avoidance behavior for phenotyping mouse models of injury and disease.

CONCLUSION

We offer a method for validating the active avoidance test, and a standard operating procedure, which will be useful in other models of neurological injury and disease.

A modified Barnes maze for an accurate assessment of spatial learning in mice

BACKGROUND

The Morris water maze (MWM) and the Barnes maze (BM) are among the most widely-used paradigms for assessing spatial learning in rodents, with specific advantages and disadvantages for each apparatus. Compared with the intense water-related stress exerted during the MWM, the BM exhibits a milder light-induced stress, while suffering from biasing animals towards non-spatial strategies such as serial search, a heuristic non-spatial search strategy. To overcome this problem, we have developed a modified Barnes maze (MBM) apparatus that recapitulates natural environments more accurately without inducing undesirable exploration strategy bias.

NEW METHOD

Apparatus. A circular 122 cm-wide table with 40 randomly placed holes. One target hole is leading to an escape chamber. Task. Three target locations were examined, varying in their distance from the center. C57BL6/j male mice were given three trials per day to find the target. Following acquisition, a probe test was performed by removing the escape chamber.

RESULTS

Spatial-encoding-depended reduction in latency to reach the target was observed, along with improvement in path efficiency with test progress. Mice tested with peripheral and distal targets outperformed mice tested with a central target. A robust exploration pattern was identified in the probe test.

COMPARISON WITH EXISTING METHOD

The MBM mimics natural environment to a higher degree of accuracy than the BM, without eliciting bias towards non-spatial searching strategies.

CONCLUSIONS

Spatial learning in the MBM is a target-location sensitive process, providing flexibility in task difficulty. Along with overcoming biases towards non-spatial strategies, the MBM represents an improvement over the well-validated BM.

Beneficial effects of xenon inhalation on behavioral changes in a valproic acid-induced model of autism in rats

BACKGROUND

Xenon (Xe) is a noble gas that has been used for the last several decades as an anesthetic during surgery. Its antagonistic effect on glutamate subtype of NMDA (N-methyl-D-aspartate) receptors resulted in evaluation of this gas for treatment of CNS pathologies, including psychoemotional disorders. The aim of this study was to assess the behavioral effects of acute inhalation of subanesthetic concentrations of Xe and to study the outcomes of Xe exposure in valproic acid (VPA)-induced rodent model of autism.

METHODS

We have conducted two series of experiments with a battery of behavioral tests aimed to evaluate locomotion, anxiety- and depression-like behavior, and social behavior in healthy, VPA-treated and Xe-exposed young rats.

RESULTS

We have shown that in healthy animals Xe exposure resulted in acute and delayed decrease of exploratory motivation, partial decrease in risk-taking and depressive-like behavior as well as improved sensorimotor integration during the negative geotaxis test. Acute inhalations of Xe in VPA-exposed animals led to improvement in social behavior, decrease in exploratory motivation, and normalization of behavior in forced-swim test.

CONCLUSION

Behavioral modulatory effects of Xe are probably related to its generalized action on excitatory/inhibitory balance within the CNS. Our data suggest that subanesthetic short-term exposures to Xe have beneficial effect on several behavioral modalities and deserves further investigation.

Selective memory and behavioral alterations after ambient ultrafine particulate matter exposure in aged 3xTgAD Alzheimer's disease mice

BACKGROUND

A growing body of epidemiological literature indicates that particulate matter (PM) air pollution exposure is associated with elevated Alzheimer's disease (AD) risk and may exacerbate AD-related cognitive decline. Of concern is exposure to the ultrafine PM (UFP) fraction (≤100 nm), which deposits efficiently throughout the respiratory tract, has higher rates of translocation to secondary organs, like brain, and may induce inflammatory changes. We, therefore, hypothesize that exposure to UFPs will exacerbate cognitive deficits in a mouse model of AD. The present study assessed alterations in learning and memory behaviors in aged (12.5 months) male 3xTgAD and non-transgenic mice following a 2-week exposure (4-h/day, 4 days/week) to concentrated ambient UFPs using the Harvard ultrafine concentrated ambient particle system (HUCAPS) or filtered air. Beginning one month following exposure, locomotor activity, spatial learning and memory, short-term recognition memory, appetitive motivation, and olfactory discrimination were assessed.

RESULTS

No effects on locomotor activity were found following HUCAPS exposure (number concentration, 1 × 104-4.7 × 105 particles/cm3; mass concentration, 29-132 μg/m3). HUCAPS-exposed mice, independent of AD background, showed a significantly decreased spatial learning, mediated through reference memory deficits, as well as short-term memory deficits in novel object recognition testing. AD mice displayed diminished spatial working memory, potentially a result of olfactory deficits, and short-term memory. AD background modulated HUCAPS-induced changes on appetitive motivation and olfactory discrimination, specifically enhancing olfactory discrimination in NTg mice. Modeling variation in appetitive motivation as a covariate in spatial learning and memory, however, did not support the conclusion that differences in motivation significantly underlie changes in spatial learning and memory.

CONCLUSIONS

A short-term inhalation exposure of aged mice to ambient UFPs at human-relevant concentrations resulted in protracted (testing spanning 1-6.5 months post-exposure) adverse effects on multiple memory domains (reference and short-term memory) independent of AD background. Impairments in learning and memory were present when accounting for potential covariates like motivational changes and locomotor activity. These results highlight the need for further research into the potential mechanisms underlying the cognitive effects of UFP exposure in adulthood.

Effects of early postnatal MK-801 treatment on behavioral properties in rats: Differences according to treatment schedule

It has been proposed that animals administered early postnatal NMDA (N-methyl-d-aspartate) glutamate receptor antagonists represent a model of schizophrenia; however, drug treatment schedules remain quite different among these animal studies. In this study, we compared the behavioral effects of long-term (14-day) and short-term (5-day) early postnatal treatment of the NMDA receptor antagonist MK-801 (dizocilpine; 5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine). In addition, different drug treatment periods were applied to the short-term treatment study in order to determine the critical developmental period of drug effects. For experiment 1, rats were treated with MK-801 (0.2 or 0.4 mg/kg, twice daily) during postnatal days (PNDs) 7-20. For experiment 2, MK-801 (0.2 mg/kg, twice daily) was administered during the periods of PNDs 7-11, 12-16, and 17-21. In adulthood, several behavioral tests, including prepulse inhibition, open-field, and spontaneous alternation tests, were performed in experiments 1 and 2. The delayed nonmatching-to-position task was also conducted in experiment 2 on separate rats treated for 5 days in the same manner. Our results indicated that the 14-day MK-801 treatment inhibited the prepulse inhibition and decreased immobility in the forced-swim test, whereas the 5-day MK-801 treatment induced only slight behavioral effects. Collectively, our findings suggest that long-term early postnatal treatment with an NMDA receptor antagonist may be detrimental to some behavioral functions, such as sensorimotor gating and stress coping; however, treatment for longer periods is needed to elicit detrimental effects.

Normal audiogram but poor sensitivity to brief sounds in mice with compromised voltage-gated sodium channels (Scn8amedJ)

The Scn8a^medJ mutation of the gene for sodium channels at the nodes of Ranvier slows nerve conduction, resulting in motor abnormalities. This mutation is also associated with loss of spontaneous bursting activity in the dorsal cochlear nucleus. However initial tests of auditory sensitivity in mice homozygous for this mutation, using standard 400-ms tones, demonstrated normal hearing sensitivity. Further testing, reported here, revealed a severely compromised sensitivity to short-duration tones of 10 and 2 ms durations. Such a deficit might be expected to interfere with auditory functions that depend on rapid processing of auditory signals.

Myelinated axons fail to develop properly in a genetically authentic mouse model of Charcot-Marie-Tooth disease type 2E

We have analyzed a mouse model of Charcot-Marie-Tooth disease 2E (CMT2E) harboring a heterozygous p.Asn98Ser (p.N98S) Nefl mutation, whose human counterpart results in a severe, early-onset neuropathy. Behavioral, electrophysiological, and pathological analyses were done on separate cohorts of Nefl^N98S/+ mutant mice and their wild type Nefl^+/+ littermates between 8 and 48 weeks of age. The motor performance of Nefl^N98S/+ mice, as evidenced by altered balance and gait measures, was impaired at every age examined (from 6 to 25 weeks of age). At all times examined, myelinated axons were smaller and contained markedly fewer neurofilaments in Nefl^N98S/+ mice, in all examined aspects of the PNS, from the nerve roots to the distal ends of the sciatic and caudal nerves. Similarly, the myelinated axons in the various tracts of the spinal cord and in the optic nerves were smaller and contained fewer neurofilaments in mutant mice. The myelinated axons in both the PNS and the CNS of mutant mice had relatively thicker myelin sheaths. The amplitude and the nerve conduction velocity of the caudal nerves were reduced in proportion with the diminished sizes of myelinated axons. Conspicuous aggregations of neurofilaments were only seen in primary sensory and motor neurons, and were largely confined to the cell bodies and proximal axons. There was evidence of axonal degeneration and regeneration of myelinated axons, mostly in distal nerves. In summary, the p.N98S mutation causes a profound reduction of neurofilaments in the myelinated axons of the PNS and CNS, resulting in substantially reduced axonal diameters, particularly of large myelinated axons, and distal axon loss in the PNS.

Cigarette smoke and nicotine effects on brain proinflammatory responses and behavioral and motor function in HIV-1 transgenic rats

Cognitive impairment in HIV-1 infection is associated with the induction of chronic proinflammatory responses in the brains of infected individuals. The risk of HIV-related cognitive impairment is increased by cigarette smoking, which induces brain inflammation in rodent models. To better understand the role of smoking and the associated immune response on behavioral and motor function in HIV infection, wild-type F344 and HIV-1 transgenic (HIV1Tg) rats were exposed to either smoke from nicotine-containing (regular) cigarettes, smoke from nicotine-free cigarettes, or to nicotine alone. The animals were then tested using the rotarod test (RRT), the novel object recognition test (NORT), and the open field test (OFT). Subsequently, brain frontal cortex from the rats was analyzed for levels of TNF-α, IL-1, and IL-6. On the RRT, impairment was noted for F344 rats exposed to either nicotine-free cigarette smoke or nicotine alone and for F344 and HIV1Tg rats exposed to regular cigarette smoke. Effects from the exposures on the OFT were seen only for HIV1Tg rats, for which function was worse following exposure to regular cigarette smoke as compared to exposure to nicotine alone. Expression levels for all three cytokines were overall higher for HIV1Tg than for F344 rats. For HIV1Tg rats, TNF-α, IL-1, and IL-6 gene expression levels for all exposure groups were higher than for control rats. All F344 rat exposure groups also showed significantly increased TNF-α expression levels. However, for F344 rats, IL-1 expression levels were higher only for rats exposed to nicotine-free and nicotine-containing CS, and no increase in IL-6 gene expression was noted with any of the exposures as compared to controls. These studies, therefore, demonstrate that F344 and HIV1Tg rats show differential behavioral and immune effects from these exposures. These effects may potentially reflect differences in the responsiveness of the various brain regions in the two animal species as well as the result of direct toxicity mediated by the proinflammatory cytokines that are produced by HIV proteins and by other factors that are present in regular cigarette smoke.

Assessment of Thermal Pain Sensation in Rats and Mice Using the Hargreaves Test

The Hargreaves test is specifically designed to assess thermal pain sensation in rodents such as rats and mice. This test has been used in experiments involving pain sensitization or recovery of thermal pain response following neural injury and regeneration. We present here a step-by-step protocol highlighted with important notes to guide first-time users through the learning process. Additionally, we have also included representative data from a rat model of sensory denervation showing how the data can be analysed to obtain meaningful results. We hope that this protocol can also assist potential users in deciding whether the Hargreaves test is a suitable test for their experiment.

Atlanto-occipital catheterization of young rats for long-term drug delivery into the lumbar subarachnoid space combined with in vivo testing and electrophysiology in situ

BACKGROUND

Catheterization has been widely used in neuroscience and pain research for local drug delivery. Though different modifications were developed, the use of young animals for spinal catheterization remains limited because of a little success rate. A reliable technique is needed to catheterize young animals aimed for in vivo testing combined with spinal cord electrophysiology, often limited by animal age, to facilitate pain research.

NEW METHODS

We describe intrathecal catheterization of young rats (3-week-old) through atlanto-occipical approach for long-lasting drug delivery into the lumbar subarachnoid space. The technique represents a surgical approach of minimized invasiveness that requires PE-10 catheter and few equipment of standard laboratory use.

RESULTS

Behavioral assessments revealed that spinal catheterization does not change peripheral sensitivity of different modalities (thermal and mechanical) and gives no rise to locomotive deficit or anxiety-like behavior in young rats. The long-term administration of genetic material (oligodeoxynucleotides given up to 4days), examined both in vivo and in situ, produced no adverse effects on basal peripheral sensitivity, but changed the AMPA receptor-mediated currents in sensory interneurons of the spinal cord.

COMPARISON WITH EXISTING METHODS

Dissimilar to already described methods, the method is designed for the use of young rats for behavioral testing in vivo and/or spinal cord electrophysiology in situ.

CONCLUSIONS

A practical method for spinal catheterization of young animals designed for studies in vivo and in situ is proposed. The method is rapid and effective and should facilitate investigation of therapeutic effects on both systemic and subcellular levels, as an advantage over the existing methods.

Neuroprotective effects of pretreatment with quercetin as assessed by acetylcholinesterase assay and behavioral testing in poloxamer-407 induced hyperlipidemic rats

Hyperlipidemia is a group of disorders characterized by excessive lipids in the bloodstream. It is associated with the incidence of cardiovascular diseases and recognized as the most important factor underlying the occurrence of atherosclerosis. This study was conducted to investigate whether pretreatment with quercetin can protect against possible memory impairment and deterioration of the cholinergic system in hyperlipidemic rats. Animals were divided into ten groups (n=7): saline/control, saline/quercetin 5mg/kg, saline/quercetin 25mg/kg, saline/quercetin 50mg/kg, saline/simvastatin (0.04mg/kg), hyperlipidemia, hyperlipidemia/quercetin 5mg/kg, hyperlipidemia/quercetin 25mg/kg, hyperlipidemia/quercetin 50mg/kg and hyperlipidemia/simvastatin. The animals were pretreated with quercetin by oral gavage for a period of 30days and hyperlipidemia was subsequently induced by intraperitoneal administration of a single dose of 500mg/kg of poloxamer-407. Simvastatin was administered after the induction of hyperlipidemia. The results demonstrated that hyperlipidemic rats had memory impairment compared with the saline control group (P<0.001). However, pretreatment with quercetin and simvastatin treatment attenuated the damage caused by hyperlipidemia compared with the hyperlipidemic group (P<0.05). Acetylcholinesterase (AChE) activity in the cerebral hippocampus was significantly (P<0.001) reduced in the hyperlipidemic group compared with the control saline group. Pretreatment with quercetin and simvastatin treatment in the hyperlipidemic groups significantly (P<0.05) increased AChE activity compared with the hyperlipidemic group. Our results thus suggest that quercetin may prevent memory impairment, alter lipid metabolism, and modulate AChE activity in an experimental model of hyperlipidemia.

Novel application of a Radial Water Tread maze can distinguish cognitive deficits in mice with traumatic brain injury

INTRODUCTION

The use of forced-swim, rat-validated cognition tests in mouse models of traumatic brain injury (TBI) raises methodological concerns; such models are vulnerable to a number of confounding factors including impaired motor function and stress-induced non-compliance (failure to swim). This study evaluated the ability of a Radial Water Tread (RWT) maze, designed specifically for mice, that requires no swimming to distinguish mice with controlled cortical impact (CCI) induced TBI and Sham controls.

METHODS

Ten-week-old, male C57BL6/J mice were randomly assigned to receive either Sham (n=14) or CCI surgeries (n=15). Mice were tested for sensorimotor deficits via Gridwalk test and Noldus CatWalk gait analysis at 1 and 32days post-injury. Mice received RWT testing at either 11days (early time point) or 35days (late time point) post-injury.

RESULTS

Compared to Sham-treated animals, CCI-induced TBI resulted in significant impairment in RWT maze performance. Additionally, CCI injured mice displayed significant deficits on the Gridwalk test at both 1day and 32days post-injury, and impairment in the CatWalk task at 1day, but not 32days, compared to Shams.

CONCLUSIONS

The Radial Water Tread maze capitalizes on the natural tendency of mice to avoid open areas in favor of hugging the edges of an apparatus (thigmotaxis), and replaces a forced-swim model with water shallow enough that the animal is not required to swim, but aversive enough to motivate escape. Our findings indicate the RWT task is a sensitive species-appropriate behavioral test for evaluating spatial memory impairment in a mouse model of TBI.

Maternal exposure to the water soluble fraction of crude oil, lead and their mixture induces autism-like behavioral deficits in zebrafish (Danio rerio) larvae

Autism spectrum disorder (ASD) is a serious debilitating mental illness with complex symptoms and multi-factorial pathogenesis. Although the pathogenesis of ASD remains unclear, etiology is thought to involve complex, multigenic interactions and possible environmental contributions. In the present study, we used zebrafish (Danio rerio) as a model to investigate whether maternal exposure to the water soluble fraction of crude oil (WSF, 5μg/L), lead (Pb, 20μg/L) and their mixture (5 μg/L WSF+20 μg/L Pb) could induce autism-like behavior in larvae. Our results showed that isolated and combined WSF/Pb exposure altered the behavioral pattern of fish swimming. WSF significantly increased anxiety and locomotor activity, decreased repetitive behavior in the open field test, and reduced the level of serotonin. However, co-exposure to WSF/Pb decreased behavioral activity and shoaling behavior, and increased cycle swimming and edge preference. Significant changes in the expression level of the multiple genes potentially critical for regulating environmental factor induced autism-like behavior were found. A gene network regulating ASD disturbed by WSF/Pb exposure was established using computational analysis. The information from the network could provide a clue for further mechanistic studies explaining molecular events regulating WSF/Pb mediated ASD.

Effects of developmental exposure to bisphenol A and ethinyl estradiol on spatial navigational learning and memory in painted turtles (Chrysemys picta)

Developmental exposure of turtles and other reptiles to endocrine disrupting chemicals (EDCs), including bisphenol A (BPA) and ethinyl estradiol (EE2, estrogen present in birth control pills), can induce partial to full gonadal sex-reversal in males. No prior studies have considered whether in ovo exposure to EDCs disrupts normal brain sexual differentiation. Yet, rodent model studies indicate early exposure to these chemicals disturbs sexually selected behavioral traits, including spatial navigational learning and memory. Thus, we sought to determine whether developmental exposure of painted turtles (Chrysemys picta) to BPA and EE2 results in sex-dependent behavioral changes. At developmental stage 17, turtles incubated at 26⁰C (male-inducing temperature) were treated with 1) BPA High (100μg /mL), 2) BPA Low (0.01μg/mL), 3) EE2 (0.2μg/mL), or 4) vehicle or no vehicle control groups. Five months after hatching, turtles were tested with a spatial navigational test that included four food containers, only one of which was baited with food. Each turtle was randomly assigned one container that did not change over the trial period. Each individual was tested for 14 consecutive days. Results show developmental exposure to BPA High and EE2 improved spatial navigational learning and memory, as evidenced by increased number of times spent in the correct target zone and greater likelihood of solving the maze compared to control turtles. This study is the first to show that in addition to overriding temperature sex determination (TSD) of the male gonad, these EDCs may induce sex-dependent behavioral changes in turtles.

Reduced long-term memory in a rat model of 8 minutes ventricular fibrillation cardiac arrest: a pilot trial

Background

Evaluating beneficial effects of potential protective therapies following cardiac arrest in rodent models could be enhanced by exploring behavior and cognitive functions. The Morris Water Maze is a well-known cognitive paradigm to test spatial learning and memory.

Results

Behavioral testing with the Morris Water Maze in Sprague–Dawley rats (300 ± 25 g) resuscitated after 8 min of ventricular fibrillation cardiac arrest was carried out 5 and 12 weeks after cardiac arrest (CA) and compared to results of naïve rats (Control).

At 5 weeks, within each group latency time to reach the hidden platform (reflecting spatial learning) decreased equally from day 1 to 4 (CA: 105.6 ± 8.2 vs. 8.9 ± 1.2 s, p < 0.001; Control: 75.5 ± 13.2 vs. 17.1 ± 4.5, p < 0.001) with no differences between groups (p = 0.138). In the probe trial 24 h after the last trial, time spent in the target sector (reflecting memory recall) within each group was significantly longer (CA: 25 ± 1.3; Control: 24.7 ± 2.5 s) than in each of the three other sectors (CA: 7.7 ± 0.7, 14.3 ± 2.5, 8.4 ± 0.8 and Control: 7.8 ± 1.2, 11.7 ± 1.5, 10.3 ± 1.6 s) but with no significantly differences between groups. Seven days later (reflecting memory retention), control group animals remained significantly longer in the target sector compared to every other sector, whereas the cardiac arrest group animals did not. Even 12 weeks after cardiac arrest, the single p values showed that the control animals displayed a trend to perform better than the resuscitated animals.

Conclusions

Memory recall was impaired early after 8 min of ventricular fibrillation cardiac arrest and might be a more valuable tool for cognitive testing than learning recall after global ischemia due to cardiac arrest.

Effects of developmental exposure to bisphenol A on spatial navigational learning and memory in rats: A CLARITY-BPA study

Bisphenol A (BPA) is a ubiquitous industrial chemical used in the production of a wide variety of items. Previous studies suggest BPA exposure may result in neuro-disruptive effects; however, data are inconsistent across animal and human studies. As part of the Consortium Linking Academic and Regulatory Insights on BPA Toxicity (CLARITY-BPA), we sought to determine whether female and male rats developmentally exposed to BPA demonstrated later spatial navigational learning and memory deficits. Pregnant NCTR Sprague-Dawley rats were orally dosed from gestational day 6 to parturition, and offspring were directly orally dosed until weaning (postnatal day 21). Treatment groups included a vehicle control, three BPA doses (2.5μg/kg body weight (bw)/day-[2.5], 25μg/kg bw/day-[25], and 2500μg/kg bw/day-[2500]) and a 0.5μg/kg/day ethinyl estradiol (EE)-reference estrogen dose. At adulthood, 1/sex/litter was tested for seven days in the Barnes maze. The 2500 BPA group sniffed more incorrect holes on day 7 than those in the control, 2.5 BPA, and EE groups. The 2500 BPA females were less likely than control females to locate the escape box in the allotted time (p value=0.04). Although 2.5 BPA females exhibited a prolonged latency, the effect did not reach significance (p value=0.06), whereas 2.5 BPA males showed improved latency compared to control males (p value=0.04), although the significance of this result is uncertain. No differences in serum testosterone concentration were detected in any male or female treatment groups. Current findings suggest developmental exposure of rats to BPA may disrupt aspects of spatial navigational learning and memory.

Repetitive Behavioral Assessments for Compound Screening in Mouse Models of Autism Spectrum Disorders

Treatments for repetitive behaviors in Autism Spectrum Disorders (ASD) and other neurodevelopmental disorders remain an unmet medical need. Mouse models are highly valuable tools for investigating the underlying pathophysiology, genetics, and neurocircuitry of ASD, and can also be characterized for ASD-related phenotypes including repetitive behaviors and stereotypies. This chapter describes methods that can be employed for the assessment of repetitive behavior phenotypes and the evaluation of the ability of test compounds to attenuate repetitive behaviors in mouse models of ASD.

Human bedside evaluation versus automatic responsiveness testing in epilepsy (ARTiE)

Evaluation of behavioral impairment during epileptic seizures is critical for medical decision making, including accurate diagnosis, recommendations for driving, and presurgical evaluation. We investigated the quality of behavioral testing during inpatient video-electroencephalography (EEG) monitoring at an established epilepsy center, and introduce a technical innovation that may improve clinical care. We retrospectively reviewed video-EEG data from 152 seizures in 33 adult or pediatric patients admitted for video-EEG monitoring. Behavioral testing with questions or commands was performed in only 50% of seizures ictally, 73% of seizures postictally, and 80% with either ictal or postictal testing combined. Furthermore, the questions or commands were highly inconsistent and were performed by nonmedical personnel in about one fourth of cases. In an effort to improve this situation we developed and here introduce Automatic Responsiveness Testing in Epilepsy (ARTiE), a series of video-recorded behavioral tasks automatically triggered to play in the patient's room by computerized seizure detection. In initial technical testing using prerecorded or live video-EEG data we found that ARTiE is initiated reliably by automatic seizure detection. With additional clinical testing we hope that ARTiE will succeed in providing comprehensive and reliable behavioral evaluation during seizures for people with epilepsy to greatly improve their clinical care.

Cognitive endophenotypes, gene-environment interactions and experience-dependent plasticity in animal models of schizophrenia

Schizophrenia is a devastating brain disorder caused by a complex and heterogeneous combination of genetic and environmental factors. In order to develop effective new strategies to prevent and treat schizophrenia, valid animal models are required which accurately model the disorder, and ideally provide construct, face and predictive validity. The cognitive deficits in schizophrenia represent some of the most debilitating symptoms and are also currently the most poorly treated. Therefore it is crucial that animal models are able to capture the cognitive dysfunction that characterizes schizophrenia, as well as the negative and psychotic symptoms. The genomes of mice have, prior to the recent gene-editing revolution, proven the most easily manipulable of mammalian laboratory species, and hence most genetic targeting has been performed using mouse models. Importantly, when key environmental factors of relevance to schizophrenia are experimentally manipulated, dramatic changes in the phenotypes of these animal models are often observed. We will review recent studies in rodent models which provide insight into gene-environment interactions in schizophrenia. We will focus specifically on environmental factors which modulate levels of experience-dependent plasticity, including environmental enrichment, cognitive stimulation, physical activity and stress. The insights provided by this research will not only help refine the establishment of optimally valid animal models which facilitate development of novel therapeutics, but will also provide insight into the pathogenesis of schizophrenia, thus identifying molecular and cellular targets for future preclinical and clinical investigations.

Behavioral assessment of NIH Swiss mice acutely intoxicated with tetramethylenedisulfotetramine

Tetramethylenedisulfotetramine (TETS) is a potent convulsant poison that is thought to trigger seizures by inhibiting the function of the type A gamma-aminobutyric acid receptor (GABAAR). Acute intoxication with TETS can cause vomiting, convulsions, status epilepticus (SE) and even death. Clinical case reports indicate that individuals who survive poisoning may exhibit long-term neuropsychological issues and cognitive deficits. Therefore, the objective of this research was to determine whether a recently described mouse model of acute TETS intoxication exhibits persistent behavioral deficits. Young adult male NIH Swiss mice received a seizure-inducing dose of TETS (0.15mg/kg, ip) and then were rescued from lethality by administration of diazepam (5mg/kg, ip) approximately 20min post-TETS-exposure. TETS-intoxicated mice typically exhibited 2 clonic seizures prior to administration of diazepam with no subsequent seizures post-diazepam injection as assessed using behavioral criteria. Seizures lasted an average of 72s. Locomotor activity, anxiety-like and depression-relevant behaviors and cognition were assessed at 1week, 1month and 2months post-TETS exposure using open field, elevated-plus maze, light↔dark transitions, tail suspension, forced swim and novel object recognition tasks. Interestingly, preliminary validation tests indicated that NIH Swiss mice do not respond to the shock in fear conditioning tasks. Subsequent evaluation of hot plate and tail flick nociception tasks revealed that this strain exhibits significantly decreased pain sensitivity relative to age- and sex-matched C57BL/6J mice, which displayed normal contextual fear conditioning. NIH Swiss mice acutely intoxicated with TETS exhibited no significant anxiety-related, depression-relevant, learning or memory deficits relative to vehicle controls at any of the time points assessed with the exception of significantly increased locomotor activity at 2months post-TETS intoxication. The general absence of long-term behavioral deficits in TETS-intoxicated mice on these six assays suggests that the neurobehavioral consequences of TETS exposure described in human survivors of acute TETS intoxication are likely due to sustained seizure activity, rather than a direct effect of the chemical itself. Future research efforts are directed toward developing an animal model that better recapitulates the SE and seizure duration reported in humans acutely intoxicated with TETS.

Langerhans cells regulate cutaneous innervation density and mechanical sensitivity in mouse footpad

Langerhans cells are epidermal dendritic cells responsible for antigen presentation during an immune response. Langerhans cells associate intimately with epidermal sensory axons. While there is evidence that Langerhans cells may produce neurotrophic factors, a role in regulating cutaneous innervation has not been established. We used genetically engineered mice in which the diphtheria toxin (DT) receptor is targeted to Langerhans cells (Lang-DTR mice) to assess sensory axon-dendritic cell interactions. Diphtheria toxin administration to wild type mice did not affect epidermal structure, Langerhans cell content, or innervation density. A DT administration regimen supramaximal for completely ablating epidermal Langerhans cells in Lang-DTR mice reduced PGP 9.5-immunoreactive total innervation and calcitonin gene related peptide-immunoreactive peptidergic nociceptor innervation. Quantitative real-time polymerase chain reaction showed that epidermal gene expression of brain derived neurotrophic factor was unchanged, but nerve growth factor and glial cell line-derived neurotrophic factor mRNAs were reduced. Behavioral testing showed that, while thermal sensitivity was unaffected, mice depleted of Langerhans cells displayed mechanical hypersensitivity. These findings provide evidence that Langerhans cells play an important role in determining cutaneous sensory innervation density and mechanical sensitivity. This may involve alterations in neurotrophin production by Langerhans or other epidermal cells, which in turn may affect mechanical sensitivity directly or as a result of neuropathic changes.

Developmental studies of the hippocampus and hippocampal-dependent behaviors: insights from interdisciplinary studies and tips for new investigators

The hippocampus is not fully developed at birth and, with respect to spatial cognition, only begins to show signs of adult-like function at three postnatal weeks in rodents. Studying the developmental period spanning roughly two to four weeks of age permits an understanding of the neural framework necessary for the emergence of spatial navigation and, quite possibly, human episodic memory. However, due to developmental factors, behavior data collection and interpretation can be severely compromised if inappropriate designs are applied. As such, we propose methodological considerations for the behavioral assessment of hippocampal function in developing rats that take into account animal size, growth rate, and sensory and motor ability. We further summarize recent key interdisciplinary studies that are beginning to unravel the molecular machinery and physiological alterations responsible for hippocampal maturation. In general, hippocampal development is a protracted process during which unique contributions to spatial cognition and complex recognition memory come "on line" at different postnatal ages creating a unique situation for elucidating the neural bases of specific components of higher cognitive abilities.

Donor age dependent graft development and recovery in a rat model of Huntington's disease: histological and behavioral analysis

Neural cell replacement therapy using fetal striatal cells has provided evidence of disease modification in clinical trials in Huntington's disease (HD) patients, although the results have been inconsistent. One of the contributing factors to the variable outcome could be the different capacity of transplanted cells derived from the primordial striatum to proliferate and maturate into striatal projection neurons. Based on the rodent lesion model of HD, the current study investigated how intrastriatal-striatal grafts from variable aged donors develop in vivo and how they influence functional recovery. Young adult female Sprague-Dawley rats were lesioned unilaterally in the dorso-striatum with quinolinic acid (0.12 M) and transplanted 14 days later with single cell suspension grafts equivalent of one whole ganglionic eminence (WGE) from donors of embryonic developmental age E13, E14, or E15; animals with or without striatal lesion served as controls. All animals were tested on the Cylinder and the Corridor tests, as well as on apomorphine-induced rotation at baseline, post-lesion/pre-grafting, and at 6 and 10 weeks post-grafting. A week prior to perfusion, a sub-group in each grafted group received fluorogold injections into the ipsilateral globus pallidus to study graft efferent projections. In summary, the data demonstrates that the age of the embryonic donor tissue has an impact on both the graft mediated functional recovery, and on the in vivo cellular composition of the striatal transplant. E13 tissue grafts gave the best overall outcome indicating that WGE from different donor ages have different potential to promote functional recovery. Understanding the stages and process in rodent striatal development could improve tissue selection in clinical trials of cell therapy in HD.