A Practical Approach, Second Edition=Ronald D. Ho.pdf

316 DEVELOPMENTAL REPRODUCTIVE TOXICOLOGY: A PRACTICAL APPROACH, SECOND EDITIONIn the overall assessment of the response, it is important to evaluate interrelated endpoints inother behavioral and/or physiological evaluations before drawing conclusions. For example, anincrease in the mean latency to escape from a straight channel during Biel maze swimmingevaluation might also be correlated with decreased motor activity, decreased peak response to anauditory stimulus, or reduced body weight. The Biel maze test evaluates a unique form of habituation.Immersion in water provides an aversive stimulus to rats. Therefore, rats must habituate tothe test conditions while also learning and remembering the escape route from the maze. It is likelythat a significant test article–related effect on habituation in locomotor activity or the auditorystartle response may also manifest itself in the early phases of the learning component of the Bielmaze test. Finally, changes in neuromotor function can negatively affect the ability to interpret allthe described assessments of learning and memory. If an animal is not able to locomote or hasimpaired motor coordination, it may be unable to perform the required tasks adequately. Thus,these data should be examined in combination with data from other measures of neuromotorfunction, such as the locomotor activity assessment or grip strength, rotarod performance, andlanding foot splay, in the functional observational battery assessment.4) Functional Observational Battery Assessments — The current FDA draft guidance forjuvenile toxicity studies 51 states that well-established methods should be used to monitor keyfunctional domains of the central nervous system and these should include assessments of reflexontogeny, sensorimotor function, locomotor activity, reactivity, and learning and memory. Many ofthese domains can be evaluated in the functional observational battery (FOB) assessment. The FOB,in combination with an automated measure of locomotor activity, was designed to quickly screenfor neurobehavioral deficits in Tier 1 adult neurotoxicity studies. 165 It has been incorporated into avariety of study designs, including acute and subchronic neurotoxicity studies, developmentalneurotoxicity studies, and more recently, nonclinical juvenile studies. 56,129,166,167 The FOB consistsof a series of endpoints that assess six functional domains, as first defined by Moser. 165 At theauthors’ testing facility, the FOB includes the parameters listed in Table 8.11.The FOB can be adapted to nonrodent species with some modifications. At the authors’laboratory, FOB testing paradigms have been developed for use in the dog and nonhuman primate,and the authors are aware of FOB tests designed for use in the rabbit. 168 Although evaluationscannot necessarily be conducted in an open-field arena for some large animal models (e.g., nonhumanprimates and rabbits), deficits in neuromotor function that may affect gait can be characterizedby modifying standard assessments used in rodents.Regardless of the animal model chosen and the specific endpoints evaluated in the FOB, it isimperative that appropriate controls (e.g., training, interobserver reliability, validation) be implementedat the testing facility. First, the investigator must ensure that observers are appropriatelytrained in the assessments, and the observer should understand the types of abnormal neurobehavioraloutcomes that may be encountered. Of equal importance, the observer must be able torecognize the normal behavior of the test species. In the authors’ laboratory, new personnel are notpermitted to be trained in the rat FOB until after a year of employment. It is our position that ittakes at least a year to develop a good understanding of normal rat behaviors, and even then, FOBtraining requires that the individual evaluate 60 control animals in addition to approximately 20animals that have been treated with various positive control agents.Another important control in the conduct of the FOB is the use of blinded examinations. Sincemany of the endpoints included in the FOB are subjective in nature, it is possible for the observerto unintentionally bias the results by applying slightly harsher expectations to animals in higherdose groups than to control animals. Therefore, neurotoxicity testing guidelines require FOBassessments to be conducted without knowledge of the animal’s dosage group assignment. 166,167The testing laboratory must also ensure that observer variability be minimized. This can beaccomplished by using only one observer for the entire study, which may not always be possible,or by conducting specialized positive control studies designed to minimize interobserver variability.© 2006 by Taylor & Francis Group, LLC