Exposure to the cytokine EGF leads to abnormal hyperactivity of pallidal GABA neurons: implications for schizophrenia and its modeling

Authors

  • Hidekazu Sotoyama,

    1. Department of Molecular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan
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  • Hisaaki Namba,

    1. Department of Molecular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan
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  • Satomi Chiken,

    1. Division of System Neurobiology, National Institute for Physiological Sciences and Department of Physiological Sciences, Graduate University for Advanced Studies, Myodaiji, Okazaki, Japan
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  • Atsushi Nambu,

    1. Division of System Neurobiology, National Institute for Physiological Sciences and Department of Physiological Sciences, Graduate University for Advanced Studies, Myodaiji, Okazaki, Japan
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  • Hiroyuki Nawa

    Corresponding author
    • Department of Molecular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan
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Address correspondence and reprint requests to Hiroyuki Nawa, Department of Molecular Neurobiology, Brain Research Institute, Niigata University, Asahimachi-dori 1-757, Niigata 951-8585, Japan. E-mail: hnawa@bri.niigata-u.ac.jp

Abstract

Previous studies on a cytokine model for schizophrenia reveal that the hyperdopaminergic innervation and neurotransmission in the globus pallidus (GP) is involved in its behavioral impairments. Here, we further explored the physiological consequences of the GP abnormality in the indirect pathway, using the same schizophrenia model established by perinatal exposure to epidermal growth factor (EGF). Single-unit recordings revealed that the neural activity from the lateral GP was elevated in EGF-treated rats in vivo and in vitro (i.e., slice preparations), whereas the central area of the GP exhibited no significant differences. The increase in the pallidal activity was normalized by subchronic treatment with risperidone, which is known to ameliorate their behavioral deficits. We also monitored extracellular GABA concentrations in the substantia nigra, one of the targets of pallidal efferents. There was a significant increase in basal GABA levels in EGF-treated rats, whereas high potassium-evoked GABA effluxes and glutamate levels were not affected. A neurotoxic lesion in the GP of EGF-treated rats normalized GABA concentrations to control levels. Corroborating our in vivo results, GABA release from GP slices was elevated in EGF-treated animals. These findings suggest that the hyperactivity and enhanced GABA release of GP neurons represent the key pathophysiological features of this cytokine-exposure model for schizophrenia.

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