The effects of sex and neonatal maternal separation on fear-potentiated and light-enhanced startle

Abstract

This study was based on the higher prevalence of anxiety disorders in women than in men, and on the finding that early adverse experiences are a major risk factor for the development of anxiety disorders later in life. The object of this study was to investigate in rats, the sensitivities of the light-enhanced startle (LES) and fear-potentiated startle (FPS) paradigms to sex differences and to determine the effects of maternal separation (MS) on the baseline startle magnitude and potentiated startle response in these paradigms. Pups in the MS group were separated daily from their mother for 180 min/day from postnatal day 2 (PND2) to PND14. Control litters remained undisturbed. The adult male and female progeny were tested in the FPS and LES. As predicted, females showed a significantly greater potentiation of startle than males in the FPS, and a strong trend towards greater startle potentiation in the LES. Contrary to predictions, MS had no effect on startle potentiation in the FPS and severely disrupted LES in female, but not male rats. The observed sex differences add to the validity of the FPS and LES as animal paradigms of fear and anxiety. The findings indicate that these paradigms can be used to study the biological basis of sex differences in fear and anxiety. In contrast, the effects of MS on startle potentiation argue against the idea that MS provides a robust model for the predicted influences of early adverse effects on these startle potentiation measures of fear and anxiety.