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Effects of lesions to the dorsal and ventral hippocampus on defensive behaviors in rats

Authors

  • Nathan S. Pentkowski,

    1. Department of Psychology, University of Hawaii, Honolulu, Hawaii, USA
    2. Pacific Biomedical Research Center, University of Hawaii, Honolulu, Hawaii, USA
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  • D. Caroline Blanchard,

    1. Pacific Biomedical Research Center, University of Hawaii, Honolulu, Hawaii, USA
    2. John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, USA
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  • Colin Lever,

    1. Department of Anatomy and Developmental Biology, University College London, UK
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  • Yoav Litvin,

    1. Department of Psychology, University of Hawaii, Honolulu, Hawaii, USA
    2. John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, USA
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  • Robert J. Blanchard

    1. Department of Psychology, University of Hawaii, Honolulu, Hawaii, USA
    2. Pacific Biomedical Research Center, University of Hawaii, Honolulu, Hawaii, USA
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N. Pentkowski, Department of Psychology, 2430 Campus Road, Gartley Hall 110, Honolulu, HI 96822-2294, USA.
E-mail: pentkows@hawaii.edu

Abstract

This study investigated the role of the hippocampus in both unconditioned and conditioned defensive behaviors by examining the effects of pretraining ibotenic acid lesions to the dorsal and ventral hippocampus in male Long–Evans hooded rats exposed to three types of threat stimuli: cat-odor, a live cat and footshock. Defensive behaviors were assessed during exposure to cat-odor and a live cat, and immediately following the presentation of footshock. Conditioned defensive behaviors were also assessed in each context 24 h after initial threat exposure. During both unconditioned and conditioned trials, dorsal hippocampal lesions failed to significantly alter any behavioral measure in each test of defense. In contrast, ventral hippocampal lesions significantly reduced unconditioned defensive behaviors during exposure to cat-odor without producing any observable effects during cat exposure. Furthermore, ventral lesions significantly attenuated conditioned defensive behaviors following the administration of footshock and during re-exposure to each context. These results suggest a specific role for the ventral, not dorsal, hippocampus in modulating anxiety-like behaviors in certain animal models of defense.

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