To measure the effect of prolonged antibiotic treatment on levels of serum corticosterone animals were treated with antibiotics via their drinking water for two weeks as described above. Animals were then analyzed in the afternoon to correlate both with peak levels of the hormone and with the time of day that behavioral endpoints were being measured. Serum was processed as above, and corticosterone concentrations were measured using a commercially available ELISA kit (Abcam). Serum samples were diluted 1:100 per manufacturer instructions.
