Acoustic startle responses of protein malnourished rats

Acoustic startle responses were measured as part of a systematic attempt to determine if early protein malnutrition leads to a general hyperreactivity to aversive stimulation. In Experiment 1 startle responses transduced by floor movements were not reliably influenced by protein restriction in the preweaning or postweaning periods. The magnitude of the startle response, however, was positively correlated with body weight, partly as a consequence of the transduction method. Thus, differences in body weight might have obscured diet-related differences in startle amplitude. In Experiment 2 startles were recorded as electromyographic responses of the neck muscles and were larger in rats fed the low protein diet postweaning, especially in rats switched from high to low protein conditions at weaning. There was no indication that rats subjected to preweaning protein malnutrition were hyperreactive to aversive stimulation. In Experiment 1 it was also found that mean startle amplitudes were larger in young adults, 60 or 90 days old, than in 35-day-old rats, partly because there was less habituation in the adults.