The effect of long context exposure on cued conditioning and c-fos expression in the rat forebrain

• Published in: Behavioural brain research 2005-06, Vol.161 (2), p.263-275
• Main Authors: Perez-Villalba, Ana, Teruel-Martí, Vicent, Ruiz-Torner, Amparo, Olucha-Bordonau, Francisco
• Format: Article
• Language: English
• Subjects: Acoustic Stimulation - adverse effects; Amygdala; Analysis of Variance; Animal; Animals; Behavior, Animal; Biological and medical sciences; c-fos; Cell Count - methods; Conditioning; Conditioning (Psychology) - physiology; Context; Cues; Diagnostic Imaging - methods; Fear; Fear conditioning; Freezing; Freezing Reaction, Cataleptic - physiology; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation - physiology; Generalization (Psychology); Hippocampus; Immunohistochemistry - methods; Learning. Memory; Male; Prosencephalon - metabolism; Proto-Oncogene Proteins c-fos - genetics; Proto-Oncogene Proteins c-fos - metabolism; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rats; Rats, Sprague-Dawley; Septum and BNST
• ISSN: 0166-4328; 1872-7549
• DOI: 10.1016/j.bbr.2005.02.028

The c-fos expression was used to study the neural substrates of the cued fear conditioning acquisition, preceded by a short exposure versus a long exposure to the conditioning context. A long-context exposure (either during the night or during the day) prior to conditioning, was associated with low freezing in the learning test. Differences in the c-fos expression of CA1, CA3, BL Amygdala, LS and BNST were found between the short- or long-context groups with a pre-exposure before cued conditioning. Ce Amygdala showed no differences in the c-fos expression labeling. We reported the hippocampal c-fos activation during the cued fear conditioning acquisition. Specifically, the CA1 activation could be related with the context–US processing during the CS–US association acquisition, which might prove that the CS–US associations cannot be made without an integrated context participating. The results showed that a long-context exposure prior to cued conditioning produces an inhibition of the CR (freezing), and this phenomenon is related with a specific c-fos expression in CA1, CA3, BL Amygdala, LS and BNST during the fear acquisition.