Elevated expression of brain-derived neurotrophic factor facilitates visual imprinting in chicks

Authors

  • Keiko Suzuki,

    1. Division of Biology, College of Liberal Arts and Sciences, Kitasato University, Sagamihara, Kanagawa, Japan
    2. Laboratory of Molecular Neuroscience, School of Biomedical Science & Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
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  • Fumihiko Maekawa,

    1. Center for Environmental Health Sciences, National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan
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  • Shingo Suzuki,

    1. Anatomy and Neurobiology, Faculty of Medicine, Kagawa University, Kagawa, Japan
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  • Tomoharu Nakamori,

    1. Division of Biology, College of Liberal Arts and Sciences, Kitasato University, Sagamihara, Kanagawa, Japan
    2. Human Frontier Science Program, Department of Health and Nutrition Sciences, Faculty of Human Health, Komazawa Women's University, Tokyo, Japan
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  • Hayato Sugiyama,

    1. Division of Biology, College of Liberal Arts and Sciences, Kitasato University, Sagamihara, Kanagawa, Japan
    2. Laboratory of Molecular Neuroscience, School of Biomedical Science & Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
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  • Tomoyuki Kanamatsu,

    1. Department of Environmental Engineering for Symbiosis, Faculty of Engineering, Soka University, Tokyo, Japan
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  • Kohichi Tanaka,

    1. Laboratory of Molecular Neuroscience, School of Biomedical Science & Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
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  • Hiroko Ohki-Hamazaki

    Corresponding author
    • Division of Biology, College of Liberal Arts and Sciences, Kitasato University, Sagamihara, Kanagawa, Japan
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Address correspondence and reprint requests to Hiroko Ohki-Hamazaki, Division of Biology, College of Liberal Arts and Sciences, Kitasato University, Sagamihara, Kanagawa 252-0373, Japan. E-mail: hamazaki@kitasato-u.ac.jp

Abstract

With the aim of elucidating the neural mechanisms of early learning, we studied the role of brain-derived neurotrophic factor (BDNF) in visual imprinting in birds. The telencephalic neural circuit connecting the visual Wulst and intermediate medial mesopallium is critical for imprinting, and the core region of the hyperpallium densocellulare (HDCo), situated at the center of this circuit, has a key role in regulating the activity of the circuit. We found that the number of BDNF mRNA-positive cells in the HDCo was elevated during the critical period, particularly at its onset, on the day of hatching (P0). After imprinting training on P1, BDNF mRNA-positive cells in the HDCo increased in number, and tyrosine phosphorylation of TrkB was observed. BDNF infusion into the HDCo at P1 induced imprinting, even with a weak training protocol that does not normally induce imprinting. In contrast, K252a, an antagonist of Trk, inhibited imprinting. Injection of BDNF at P7, after the critical period, did not elicit imprinting. These results suggest that BDNF promotes the induction of imprinting through TrkB exclusively during the critical period.

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