The Future of Neurotoxicology: A Neuroelectrophysiological Viewpoint.

David W Herr

doi:10.3389/ftox.2021.729788

Abstract

Neuroelectrophysiology is an old science, dating to the 18th century when electrical activity in nerves was discovered. Such discoveries have led to a variety of neurophysiological techniques, ranging from basic neuroscience to clinical applications. These clinical applications allow assessment of complex neurological functions such as (but not limited to) sensory perception (vision, hearing, somatosensory function), and muscle function. The ability to use similar techniques in both humans and animal models increases the ability to perform mechanistic research to investigate neurological problems. Good animal to human homology of many neurophysiological systems facilitates interpretation of data to provide cause-effect linkages to epidemiological findings. Mechanistic cellular research to screen for toxicity often includes gaps between cellular and whole animal/person neurophysiological changes, preventing understanding of the complete function of the nervous system. Building Adverse Outcome Pathways (AOPs) will allow us to begin to identify brain regions, timelines, neurotransmitters, etc. that may be Key Events (KE) in the Adverse Outcomes (AO). This requires an integrated strategy, from in vitro to in vivo (and hypothesis generation, testing, revision). Scientists need to determine intermediate levels of nervous system organization that are related to an AO and work both upstream and downstream using mechanistic approaches. Possibly more than any other organ, the brain will require networks of pathways/AOPs to allow sufficient predictive accuracy. Advancements in neurobiological techniques should be incorporated into these AOP-base neurotoxicological assessments, including interactions between many regions of the brain simultaneously. Coupled with advancements in optogenetic manipulation, complex functions of the nervous system (such as acquisition, attention, sensory perception, etc.) can be examined in real time. The integration of neurophysiological changes with changes in gene/protein expression can begin to provide the mechanistic underpinnings for biological changes. Establishment of linkages between changes in cellular physiology and those at the level of the AO will allow construction of biological pathways (AOPs) and allow development of higher throughput assays to test for changes to critical physiological circuits. To allow mechanistic/predictive toxicology of the nervous system to be protective of human populations, neuroelectrophysiology has a critical role in our future.

Highlights

A proposal of future directions for application of neuroelectrophysiological techniques in toxicology must define some of the current and future problems facing the science of neurotoxicology
(and in the foreseeable future), two major emphases in the field of neurotoxicology are: 1) mechanistic information and 2) human cognitive alterations (including diseases such as attention deficit hyperactivity disorder (ADHD), autism, learning disabilities, motor and sensory deficits, etc.). Both areas can be advanced through the systematic collection of targeted functional mechanistic data based on known or presumed biological pathways (Adverse Outcome Pathways (AOPs) in the field of neurotoxicology)
Optogenetic re-activation of dentate gyrus neurons that were first activated during fear conditioning, induced freezing behavior in a different environmental context—indicating that these specific neurons were contributing to the memory engram (Liu et al, 2012)

Summary

Introduction

A proposal of future directions for application of neuroelectrophysiological techniques in toxicology must define some of the current and future problems facing the science of neurotoxicology. (and in the foreseeable future), two major emphases in the field of neurotoxicology are: 1) mechanistic information and 2) human cognitive alterations (including diseases such as attention deficit hyperactivity disorder (ADHD), autism, learning disabilities, motor and sensory deficits, etc.). Both areas can be advanced through the systematic collection of targeted functional mechanistic data based on known or presumed biological pathways (Adverse Outcome Pathways (AOPs) in the field of neurotoxicology). The collection of mechanistic data to understand the function of the nervous system has been occurring for a long time.

Methods

Conclusion