Developmental neurotoxicity testing requirements

More in-depth behavioral tests are required if dose-related toxicant effects are noted in screening tests. These tests may also be required as part of more selective toxicological screening, such as for developmental neurotoxicity. Focused tests of neuromotor function and activity, sensory functions, memory, attention, and motivation help to identify sites of toxicant-mediated lesioning, aid in the classification of neurotoxicants, and may suggest mechanisms of action. Some of these tests, like the schedule-controlled operant behavior tests for cognitive function, require animal training and extensive operator interaction with the animals. 

Neurotoxicity is of great significance in toxicology, however, and tests have been devised to supplement those routinely required. These include acute and subchronic neurotoxicity studies as well as developmental neurotoxicity studies. 

Some of these side effects may be impossible to detect either in vivo or using alternative model systems nevertheless, the availability of models that would be predictive of neurotoxic effect is of great relevance for the risk assessment of existing chemicals and of new molecular entities. In vivo testing guidelines for neurotoxicity and developmental neurotoxicity have been developed, implemented, and validated. Though there is still room for improvements and refinements, these in vivo tests have been shown, so far, to provide reliable indications on the potential neurotoxicity of chemical substances. However, such in vivo tests are time consuming and expensive and require the use of a substantial number of animals. 

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