Roadbumps at the Crossroads of Integrating Behavioral and In Vitro Approaches for Neurotoxicity Assessment

Abstract

With the appreciation that behavior represents the integration and complexity of the nervous system, neurobehavioral phenotyping and assessment has seen a renaissance over the last couple of decades, resulting in a robust database on rodent performance within various testing paradigms, possible associations with human disorders, and therapeutic interventions. The interchange of data across behavior and other test modalities and multiple model systems has advanced our understanding of fundamental biology and mechanisms associated with normal functions and alterations in the nervous system. While there is a demonstrated value and power of neurobehavioral assessments for examining alterations due to genetic manipulations, maternal factors, early development environment, the applied use of behavior to assess environmental neurotoxicity continues to come under question as to whether behavior represents a sensitive endpoint for assessment. Why is rodent behavior a sensitive tool to the neuroscientist and yet, not when used in pre-clinical or chemical neurotoxicity studies? Applying new paradigms and evidence on the biological basis of behavior to neurobehavioral testing requires expertise and refinement of how such experiments are conducted to minimize variability and maximize information. This review presents relevant issues of methods used to conduct such test, sources of variability, experimental design, data analysis, interpretation, and reporting. It presents beneficial and critical limitations as they translate to the in vivo environment and considers the need to integrate across disciplines for the best value. It proposes that a refinement of behavioral assessments and understanding of subtle pronounced differences will facilitate the integration of data obtained across multiple approaches and to address issues of translation.

Protocols for the Evaluation of Neurodevelopmental Alterations in Rabbit Models In Vitro and In Vivo

“…However, in developmental neurotoxicity studies, to avoid previously described effects of serious exaggeration of significant effects in treated groups (Haseman and Hogan, 1975), the statistical unit of measure should be the litter and not the pup as also recommended in OECD TG 426 (OECD, 2007). For further discussion about this, the authors are referred to Harry et al (2022), and articles included in this special issue.…”

New approach methods to assess developmental and adult neurotoxicity for regulatory use: a PARC work package 5 project

“…As dedicated DNT studies are often complex studies using rodents, they are resource-intensive regarding time, costs, and number of animals ( Crofton et al, 2012 ; Smirnova et al, 2014 ) and only a limited number of chemicals have been tested for DNT using OECD TG DNT studies ( OECD, 2008a ; Makris et al, 2009 ; Sachana et al, 2019 ; Crofton and Mundy, 2021 ). In addition, variability in rodent neurotoxicity tests has been documented ( Tsuji and Crofton, 2012 ; Terron and Bennekou, 2018 ; Sachana et al, 2019 ; Paparella et al, 2020 ; Harry et al, 2022 ) which indicates a need to specify, optimize, and harmonize the individual test methods used as part of the OECD TG. It also underscores the need for new tests that lack the excess variability associated with in vivo guideline studies for the assessment of DNT.…”

“…A fundamental requirement for the regulatory acceptance of NAMs involves the development of test methods characterized by a high degree of robustness, performance, and readiness ( Bal-Price et al, 2018 ), including acceptable levels of variability ( Harry et al, 2022 ). If they are intended for future use in the context of hazard assessment, NAMs should ideally meet or exceed the sensitivity, specificity, accuracy, and reliability of the respective OECD TG, to ensure a continued level of acceptable chemical safety ( Bal-Price et al, 2018 ).…”

Behavioral Effects of Exposure to Phthalates in Female Rodents: Evidence for Endocrine Disruption?

“…Different types of learning and memory processes rely on various synaptic plasticity mechanisms and depend on several brain areas, among which, in [ 36 , 37 ], the hippocampus was shown to play a key role in spatial memory, nonspatial memory such as visual object recognition, and temporal processing of information. Behavioral tests assessing these different aspects of learning and memory are widely used in rodents including in the field of neurotoxicology [ 38 ].…”