There are No Sex-Specific Differences in Habituation and Prepulse Inhibition of Acoustic Startle Response in Sprague Dawley Rats

Habituation is characterized by a gradual decrease in response to a repeated, irrelevant stimulus. In rodents, habituation can be studied using the acoustic startle response (ASR). ASR can also be modulated by prepulse inhibition (PPI), where the presentation of a sub-threshold pre-stimulus decreases an organism’s behavioural response to a subsequent high intensity stimulus. While sex-specific differences in habituation and PPI have been observed in humans in association with several disorders, such as bipolar disorder and schizophrenia, they have not been extensively studied in a healthy model in Sprague Dawley rats. Pre-existing sex-specific differences have important implications for characterizing diseases on the basis of non-associative learning deficits. Furthermore, female subjects are often excluded from non-associative learning experiments due to potential effects of hormonal fluctuations on startle modulations. The focus of this study was to investigate any sex differences in startle modulations with the hope of addressing any experimental concerns with the use of females in non-associative learning experiments. This experiment observed short-term habituation and PPI in male and female Sprague Dawley rats from postnatal day 12 to 40. Habituation was assessed through the presentation of a high intensity (105 db) acoustic stimulus for twenty trials, with stimulus duration of 20ms per trial. PPI was measured through exposure to a prepulse of three possible intensities (0 db, 75 db, 80 db) for duration of 4 ms, followed by exposure to the pulse (105 db), with an ISI of 50 ms. There was no significant difference in prepulse inhibition between sex. Similarly, there was no significant sex difference in habituation. This experiment indicates that habituation and prepulse inhibition are not significantly affected by gender differences, perhaps due in part to the adaptive nature of non-associative learning.