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.