Okio Arai

Dokkyo University, Edo, Tōkyō, Japan

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Publications (3)4.23 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The central nervous system is highly sensitive to endogenous and exogenous chemicals. Catecholamines, norepinephrine (NE) and dopamine (DA), regulate many different brain functions including learning and memory, emotion, stress responses and homeostatic control of physiological systems. NE and DA are differently involved in reward-related neuronal activity and other task-related neuron activities in the prefrontal cortex, amygdala and the lateral hypothalamic area. During inflammatory and non-inflammatory stress conditions, NE levels are locally regulated at terminal levels by proinflammatory cytokines such as interleukin-1β in which prostanoid and nitric oxide are involved. NE system has been shown to express estrogen receptors and is highly sensitive to endocrine disrupters such as bisphenol A during sexual differentiation. These findings suggest that higher brain functions such as learning and emotional control are under the influence of chemical impacts via catecholamines, cytokines and environmental chemicals.
    International Congress Series 01/2004; 1269:101-104.
  • [Show abstract] [Hide abstract]
    ABSTRACT: There is an endocrinological concern that environmental endocrine disrupters (EEDs) may influence sexual differentiation. Bisphenol A (BPA), one of EEDs, is released from polycarbonate plastics, and has been detected in the human umbilical cord. In this study, we examined the effect of BPA on the sexual differentiation of open-field behavior and the sexually dimorphic nuclei in the brain in the offspring of rats exposed to BPA during the fetal and suckling periods at a dosage below the human tolerable daily intake (TDI) level. In the control group, females were more active in the open field and had a larger locus coeruleus (LC) volume than males. BPA abolished and inverted the sex differences of the open-field behavior and the LC volume, respectively, without affecting the reproductive system. We also compared the effects of estrogenic compounds, diethylstilbestrol (DES) and resveratrol (RVT), to that of BPA because of their structural similarities. DES affected the open-field behavior, LC volume and reproductive system, while RVT affected the LC volume and the reproductive system. These results suggest that the brain is highly sensitive to BPA at a dosage below TDI and that the disrupting effects of BPA on sexual differentiation may vary from those of RVT and DES.
    Neuroscience Research 04/2003; 45(3):345-56. · 2.20 Impact Factor
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    ABSTRACT: This study tested the effect of exposure to bisphenol A (BPA) early in life on the sexual differentiation in the brain and behavior in Wistar rats. We administered BPA only to mother rats during pregnancy and lactation at a dosage of approximately 1.5 mg/kg per day far less than the no-observed-adverse-effect level (NOAEL; 50 mg/kg per day). Control female offspring showed a higher activity, a lower avoidance memory, and larger locus coeruleus than the male controls, while the BPA-exposed group did not show any sexual dimorphism. BPA did not affect the reproductive organs or sex hormones. Our results suggest that the current methods to determine the NOAEL of artificial industrial chemicals may not be sufficient to detect a disruption of the sexual differentiation in the brain.
    Neuroscience Letters 06/2001; 304(1-2):73-6. · 2.03 Impact Factor

Publication Stats

226 Citations
4.23 Total Impact Points

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Institutions

  • 2004
    • Dokkyo University
      Edo, Tōkyō, Japan
  • 2001–2003
    • Dokkyo Medical University
      • Department of Physiology and Biological Information
      Totigi, Tochigi, Japan