Table 1.

Examples of potential endpoints for developmental and adult neurotoxicity in animal studies (adapted and modified from EPA [4]).

Endpoints	Examples of indicators of neurotoxic effect
Behavioral	Delays in the ontogeny of behaviors
	Changes in clinical signs (e.g., touch, sight, sound, motor coordination, weakness, paralysis, abnormal movement or posture, tremor, seizures, body temperature)
	Altered grip strength or limb splay
	Increases or decreases in motor activity
	Increases or decreases in amplitude or latency of sensorimotor reflex
	Changes in learning, memory, and attention
Neurophysiological	Changes in velocity, amplitude, or refractory period of nerve conduction
	Changes in latency or amplitude of sensory-evoked potential
	Changes in electroencephalographic patterns
Neurochemical	Alterations in synthesis, release, uptake, degradation of neurotransmitters
	Alterations in second-messenger-associated signal transduction
	Alterations in membrane-bound enzymes regulating neuronal activity
	Inhibition and aging of neuropathy target esterase Increases in glial fibrillary acidic protein in adults
Structural or neuropathological	Gross changes in morphology, including brain weight Quantitative and qualitative histologic changes in neurons or glia (neuronopathy, axonopathy, myelinopathy)