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Acoustic Startle Response in the Study of Developmental Toxicity

Acoustic startle response (ASR) is a defensive reflex that occurs shortly after presentation of a brief intense acoustic stimulus. It consists of a sudden contraction of facial and skeletal muscle. ASR in rodents is a gross vibration‐like movement of the body that is easy to elicit, record, and analyze quantitatively. It can also be used as a reliable and sensitive measure of physiological mechanism of developmental toxicity. The basic neural mechanisms of ASR have been elucidated. The cochlear nucleus and the reticular nucleus of pons are essential to the induction and regulation of ASR amplitude. Fear or anxiety augments ASR (fear potentiation) and functionally involves amygdala. A brief presentation of a weak acoustic stimulus shortly before the presentation of a startling stimulus suppresses ASR (prepulse inhibition). Prepulse inhibition is thought to be regulated by the dopaminergic mesolimbic system. Taken together, these phenomena suggest the use of ASR as a means of modeling anxiety/fear and the sensorymotor abnormalities that may present themselves in a condition such as schizophrenia. In this review, the fundamental behavioral and neural features of ASR are described and major findings in connection with the toxicology of ASR are reviewed. Finally, the significance of ASR in the study of developmental toxicology including behavioral teratology is discussed. Key words: acoustic startle response, fear potentiation, prepulse inhibition, developmental toxicology, behavioral teratology