Role of Animal Models in Parkinson's Disease (PD): What Role They Play in Preclinical Translational Research

BACKGROUND

Animal models for drug discovery and development in Parkinson 's disease have played an important role in the characterization of the pathophysiology of diseases and associated mechanisms of injury, drug target identification, and evaluation of novel therapeutic agents for toxicity/ safety, pharmacokinetics, pharmacodynamics, and efficacy.

OBJECTIVE

The review is intended to reform the scope, advantages, and limitations of various Parkinson's Disease models and their scope in translational research. The lack of a gold standard for PD animal models presents a major challenge in devising a validation system. This review is an attempt to provide a way to adopt the validation approach for PD animal model for research.

METHODS

Because underlying disease mechanisms are so similar across species, it is possible to extrapolate results from Parkinson's disease studies using animal models. Furthermore, behavioural tests used to access the neurobehavioral test with its limitations were explored for rodents, non-human primates, lower-order animals, and invertebrates. The role of gender selectivity and non-selectivity is the one major concern in PD model validation that is addressed in the review.

RESULTS

The rigorous validation has been done on animal models for Parkinson's disease (PD) based on comparisons to the human state. Regarding toxicological and safety investigations in PD, non-animal options must be thoroughly validated. There are both advantages and disadvantages to using animal models of Parkinson's disease as proof-of-concept research.

CONCLUSION

The specific animal model selected for a given drug to be tested and developed depends on the goal of the specific study.

Nasal obstruction during the growth period modulates the Wnt/β-catenin pathway and brain-derived neurotrophic factor production in association with tyrosine kinase receptor B mRNA reduction in mouse hippocampus

There is accumulating evidence that nasal obstruction induces high‐level brain dysfunction, including memory and learning deficits. We previously demonstrated that unilateral nasal obstruction (UNO) during the growth period increases the expression of brain‐derived neurotrophic factor (BDNF). The expression of BDNF is regulated by the Wnt/β‐Catenin pathway, which is linked to neuronal differentiation, proliferation, and maintenance. However, little is known about whether Wnt3a protein expression could be an index for modulations analyses in the Wnt/β‐Catenin pathway caused by UNO during the growth period. This study aimed to investigate the effects of UNO during the growth period on the Wnt/β‐Catenin pathway in the hippocampus using combined behavioural, biochemical, and histological approaches. Male BALB/C mice were randomly divided into the control (CONT; n = 6) and experimental (UNO; n = 6) groups. Blood oxygen saturation (SpO₂) levels were measured, and a passive avoidance test was performed in mice aged 15 weeks. Brain tissues were subjected to immunohistochemistry, real‐time reverse transcription‐polymerase chain reaction, and western blot analysis. Compared with control mice, UNO mice had lower SpO₂ levels and exhibited memory/learning impairments during behavioural testing. Moreover, Wnt3a protein, BDNF mRNA, and tyrosine kinase receptor B (TrkB) mRNA expression levels were significantly lower in the hippocampus in the UNO group than in the CONT group. Our findings suggested that UNO during the growth period appeared to modulate the hippocampal Wnt/β‐catenin pathway and BDNF production in association with TrkB mRNA reduction, thereby resulting in memory and learning impairments.

Exploratory Behaviours of Primitive Horses Based on Konik: A Preliminary Study

This study aimed at assessing the behaviour of Konik geldings and mares, kept in a stable and in a free-range system, during behavioural tests regarded as a determinant of the exploration urge. A total of 19 Konik horses kept in individual stables and in a free-range system were included in the study. The experiment was conducted in five phases separated by five-day breaks. A one-stage passive human test was performed during the first phase, a three-stage active human test-2nd phase, a three-stage unknown object test-3rd phase, a two-stage unknown surface test-4th phase, and a one-stage test of social isolation-5th phase. Ten attributes were analysed, including the horse sex and the keeping system. The results were also correlated with one another. Konik horses were found to show the urge to explore, although their behavioural responses are individual and stimulus dependent. In many cases, the horse sex and the keeping system influence the exploratory behaviour, although it is manifested by a greater intensity in geldings than in mares, and in free-range horses than in those kept in a stable. The study is regarded as preliminary due to the small number of horses in the study groups.

The onset of piscivory in a freshwater fish species: analysis of behavioural and physiological traits

The onset of piscivory in fish, resulting in a shift from zooplankton or invertebrate to fish prey, was studied on pikeperch (Sander lucioperca) larvae displaying and not displaying piscivorous behaviour at different ages (23, 30, 37, 44 and 52 days post-hatching) using behavioural (attack, capture and swimming activity), morphological (allometry) and digestive enzymatic (trypsin, α-amylase and pepsin) analyses. The shift from zooplanktonic food items (Artemia nauplii) to a piscivorous diet did not occur at the same time for all individuals within the same cohort. Predation tests, conducted under controlled conditions (20°C; ad libitum feeding), showed that some larvae attacked fish prey as early as the age of 3 weeks [11.0 ± 1.3 mm total length (TL)], whereas others did not start until the age of 6 weeks (16.6 ± 1.9 mm TL). Piscivorous individuals were bigger, with larger heads, longer tails, higher acid protease and lower alkaline protease activities, than non-piscivorous conspecifics. In conclusion, high interindividual variability in morphological and digestive system developments linked to the development of predatory abilities could induce cannibalism in fish.

Review: Neuropathology and behavioural features of transgenic murine models of Alzheimer's disease

Our understanding of the underlying biology of Alzheimer's disease (AD) has been steadily progressing; however, this is yet to translate into a successful treatment in humans. The use of transgenic mouse models has helped to develop our understanding of AD, not only in terms of disease pathology, but also with the associated cognitive impairments typical of AD. Plaques and neurofibrillary tangles are often among the last pathological changes in AD mouse models, after neuronal loss and gliosis. There is a general consensus that successful treatments need to be applied before the onset of these pathologies and associated cognitive symptoms. This review discusses the different types of AD mouse models in terms of the temporal progression of the disease, how well they replicate the pathological changes seen in human AD and their cognitive defects. We provide a critical assessment of the behavioural tests used with AD mice to assess cognitive changes and decline, and discuss how successfully they correlate with cognitive impairments in humans with AD. This information is an important tool for AD researchers when deciding on appropriate mouse models, and when selecting measures to assess behavioural and cognitive change.

A Systematic Review of the Reliability and Validity of Behavioural Tests Used to Assess Behavioural Characteristics Important in Working Dogs

Background

Working dogs are selected based on predictions from tests that they will be able to perform specific tasks in often challenging environments. However, withdrawal from service in working dogs is still a big problem, bringing into question the reliability of the selection tests used to make these predictions.

Methods

A systematic review was undertaken aimed at bringing together available information on the reliability and predictive validity of the assessment of behavioural characteristics used with working dogs to establish the quality of selection tests currently available for use to predict success in working dogs.

Results

The search procedures resulted in 16 papers meeting the criteria for inclusion. A large range of behaviour tests and parameters were used in the identified papers, and so behaviour tests and their underpinning constructs were grouped on the basis of their relationship with positive core affect (willingness to work, human-directed social behaviour, object-directed play tendencies) and negative core affect (human-directed aggression, approach withdrawal tendencies, sensitivity to aversives). We then examined the papers for reports of inter-rater reliability, within-session intra-rater reliability, test-retest validity and predictive validity.

Conclusions

The review revealed a widespread lack of information relating to the reliability and validity of measures to assess behaviour and inconsistencies in terminologies, study parameters and indices of success. There is a need to standardise the reporting of these aspects of behavioural tests in order to improve the knowledge base of what characteristics are predictive of optimal performance in working dog roles, improving selection processes and reducing working dog redundancy. We suggest the use of a framework based on explaining the direct or indirect relationship of the test with core affect.

Bergamot Essential Oil Attenuates Anxiety-Like Behaviour in Rats

Preclinical studies have recently highlighted that bergamot essential oil (BEO) is endowed with remarkable neurobiolological effects. BEO can affect synaptic transmission, modulate electroencephalographic activity and it showed neuroprotective and analgesic properties. The phytocomplex, along with other essential oils, is also widely used in aromatherapy to minimize symptoms of stress-induced anxiety and mild mood disorders. However, only limited preclinical evidences are actually available. This study examined the anxiolytic/sedative-like effects of BEO using an open field task (OFT), an elevated plus-maze task (EPM), and a forced swimming task (FST) in rats. This study further compared behavioural effects of BEO to those of the benzodiazepine diazepam. Analysis of data suggests that BEO induces anxiolytic-like/relaxant effects in animal behavioural tasks not superimposable to those of the DZP. The present observations provide further insight to the pharmacological profile of BEO and support its rational use in aromatherapy.

Ozone degrades floral scent and reduces pollinator attraction to flowers

In this work we analyzed the degradation of floral scent volatiles from Brassica nigra by reaction with ozone along a distance gradient and the consequences for pollinator attraction. For this purpose we used a reaction system comprising three reaction tubes in which we conducted measurements of floral volatiles using a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) and GC-MS. We also tested the effects of floral scent degradation on the responses of the generalist pollinator Bombus terrestris. The chemical analyses revealed that supplementing air with ozone led to an increasing reduction in the concentrations of floral volatiles in air with distance from the volatile source. The results revealed different reactivities with ozone for different floral scent constituents, which emphasized that ozone exposure not only degrades floral scents, but also changes the ratios of compounds in a scent blend. Behavioural tests revealed that floral scent was reduced in its attractiveness to pollinators after it had been exposed to 120 ppb O3 over a 4.5 m distance. The combined results of chemical analyses and behavioural responses of pollinators strongly suggest that high ozone concentrations have significant negative impacts on pollination by reducing the distance over which floral olfactory signals can be detected by pollinators.

Maternal zinc supplementation improves spatial memory in rat pups

A large body of evidence supports an opinion that adequate dietary zinc is essential for prenatal and postnatal brain development. Behavioural effects of maternal supplementation with ZnSO(4) were analysed in rat pups with the Morris water task performance, a hole board and a T-maze. Wistar females during pregnancy and lactation received a drinking water solution of ZnSO(4) at doses of 16 mg/kg (group Zn16) or 32 mg/kg (group Zn32). Behavioural tests were conducted on the 4-week-old male rat pups. Zinc concentration in the serum, hippocampus and prefrontal cortex of offsprings was determined by means of atomic absorption techniques. The Newman-Keuls multiple comparison test revealed an increase of climbing in the Zn16 group in comparison to the control group (Con) and the Zn32 group during the hole board test. ANOVA for repeated measures showed a significant memory improvement in both supplemented groups compared to the control in the probe trial on day 5 of the water maze test. ZnSO(4) treatment significantly elevated zinc levels in the rat serum. Follow-up data on brain content of zinc in the hippocampus revealed significant differences between the groups and in supplemented groups correlated with crossings above the original platform position. These findings suggest that pre- and postnatal zinc supplementation may improve cognitive development in rats.