Auditory Fear Conditioning and Conditioned Stress Raise NO<sub>3</sub><sup>

Vol. 53, No. 3, 2006

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Original Paper

Auditory Fear Conditioning and Conditioned Stress Raise NO₃^- Level in the Amygdala
Taku Sato^a, Eiji Suzuki^a, Masamoto Yokoyama^a, Shigeru Watanabe^b, Hitoshi Miyaoka^a

^aDepartment of Psychiatry and
^bDivision of Biophysics, Kitasato University School of Medicine, Sagamihara, Japan

Address of Corresponding Author

Neuropsychobiology 2006;53:142-147 (DOI: 10.1159/000093100)

Key Words

Fear conditioning
Conditioned stress
Nitric oxide
Amygdala

Abstract

Background: The conditioned fear response is considered to be acquired by experimental animals when tone information is combined with that of an electrical foot shock (unconditioned stimulus) in the amygdala. Nitric oxide biosynthesized in the brain is reportedly involved in several kinds of learning. Methods: In this study, we continuously monitored the NO₃^- level, as a marker of nitric oxide production, in the amygdala starting before the application of tone and electrical foot shock stimuli together (conditioned group) or the tone stimulus alone (control group) on day 1, until after the tone information was given (both groups) on day 2, using the in vivo microdialysis method. Results: The NO₃^- level of the conditioned group was increased on both day 1 and day 2, while that of the control group was not elevated on either day. Freezing behavior was observed in the conditioned but not the control rats. Conclusions: Although the sources of NO₃^- remain uncertain, these results suggest that nitric oxide is associated with auditory fear conditioning and the response to a conditioned stimulus.

Author Contacts

Eiji Suzuki, MD, PhD
Department of Psychiatry
Kitasato University School of Medicine
2-1-1 Asamizodai, Sagamihara, 228-8520 (Japan)
Tel. +81 42 748 9111, Fax +81 42 765 3570, E-Mail e-suzuki@kitasato-u.ac.jp

Article Information

Received: October 25, 2005
Accepted after revision: March 2, 2006
Published online: May 4, 2006
Number of Print Pages : 6
Number of Figures : 3, Number of Tables : 0, Number of References : 24

Medline Abstract (ID 16679778)

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