Differences in response to an acoustic startle stimulus among forty-six rat strains

The startle response to intense environmental stimuli is found in most, if not all, animal species. Previous studies have shown that selected rodent strains differ in startle response to an acoustic stimulus, suggesting genetic variability. The current experiment was designed to extend these differences to a wider range of rat strains. Forty-six inbred and outbred rat strains were studied. These strains exhibited differences in both the mean amplitude of the startle response and the rate of habituation to startle stimuli over repeated trials. In addition, there was a significant relationship between these measures. These results suggest that robust phenotypic differences in startle response exist among rat strains. As previous investigations have demonstrated a direct relationship between the startle response and other behavioral end points, the use of strain differences in startle response may be an effective way to determine genetic contributions to specific behavioral responses.