Stress induction
Animals were handled and acclimatized to the experimenter and all
apparatuses for 3 days before testing to reduce anxiety-like symptoms
or stress. Exposure to unpredictable sound stress occurred over 3 days
as described previously (Khasar et al., 2009; Khasar et al., 2008).
Animals were placed 4-5 per cage and the cage placed 25 cm from a
speaker that emitted 4 pure tones (5, 11, 15, and 19 kHz), whose
amplitudes varied through time independently from 20−110 dB sound
pressure level at random times each minute, lasting 5 or 10 seconds.
Non-stressed (NST) animals were placed in the sound chamber for 30
minutes but without exposure to the sound stimulus. Following sound or
non-stress, mice were returned to their home cages in the animal care
facility.