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Neural Plasticity
Volume 10 (2003), Issue 4, Pages 327-333
Short Communication

Enhancement of Latent Inhibition by Chronic Mild Stress in Rats Submitted to Emotional Response Conditioning

1Laboratório de Sistemas Neurais e Comportamento, Departamento de Fisiologia e Biofisica, IB, Universidade Estadual de Campinas, Cidade Universitária Prof. Zeferino Vaz, Campinas, SP 13083-970, Brazil
2Unidade Acadêmica da Área de Ciências Biológicas e da Saúde, Universidade São Francisco, Av. São Francisco de Assis, Bragança Paulista, SP 12916-900, Brazil
3Departamento de Farmacologia, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, Cidade Universitária Prof. Zeferino Vaz, Campinas, SP 13083-970, Brazil
4Laboratoire de Psychopathologie et de Psychopharmacologie de la Cognition, U 405 INSERM, Institut de Physiologie, Faculté de Médecine, Université Louis Pasteur,11 rue Humann, Strasbourg Cédex F-67085, France

Copyright © 2003 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This work evaluated the influence of chronic mild stress on latent inhibition (LI) in rats, using a conditioned emotional response (CER) procedure. Rats were assigned to four groups: a non pre-exposed control group (NPC), a non pre-exposed stressed group (NPS), a preexposed control group (PC), and a pre-exposed stressed group (PS). Stressed animals were submitted to a chronic mild stress (CMS) regimen for three weeks. The off-baseline conditioned emotional response procedure had four phases: licking response training, tone- shock conditioning, retraining, and testing. Conditioning consisted of 2 tone (30 s) and shock (0.5 s) associations. Tone-shock conditioning evidenced by NPS and NPC groups suggests that stress did not interfere with the expression of a conditioned emotional response. Pre-exposure was carried out using 6 tones (30 s) during 2 sessions before conditioning. Prior exposure to the tone resulted in a decrease in learning that was greater in stressed animals. The results indicate an increase in latent inhibition induced by chronic mild stress. Such LI potentiation after CMS may be related to dopamine (DA) neurotransmission reduction in the central nervous system.