Contextual fear conditioning test
The contextual fear conditioning test was performed as described by Onishi and Xavier (Onishi and Xavier, 2010) with modifications. During the contextual training phase, each rat received ten footshocks (2.0 mA) with intervals of 20 s between the footshocks. Twenty-four hours after training, rats were individually transported to the experimental room and placed into the training chamber where they were maintained for 5 min. The time the animals spent exhibiting freezing during this session was measured. Freezing was considered as a “body immobility and the absence of vibrissae movement associated with sniffing”
(Bouton and Bolles, 1980). At the end of the 5 min session the animals
were removed from the chamber and returned to their home cages.