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J.Health Sci., 50(4), 407-412, 2004
Intracisternal Administration of p-n-Octylphenol into Neonatal Rats Causes Hyperactivity Concomitantly with the Terminal Deoxynucleotidyl Transferase-Mediated dUTP Nick End-Labelling (TUNEL)-Positive Cells in the Mesencephalon where Immunoreactivity for Tyrosine Hydroxylase is Reduced by the Chemical
Masami Ishido,*, a Yoshinori Masuo,b Syuichi Oka,b Etsuo Niki,c and Masatoshi Moritaa
aEndocrine Disruptors and Dioxin Research Projects, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan, bHuman Stress Signal Research Center (HSS), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8566, Japan, and cHSS, AIST, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan
It is unknown which endocrine disruptors exert their effects on neuronal functions, particularly leading to behavioral alterations. To address this, we examined the effects of p-n-octylphenol, an endocrine disruptor, on rat behavior and cellular responses. Single intracisternal administration of p-n-octylphenol (87 nmol) into 5-day-old male Wistar rats caused significant hyperactivity at 4-5 weeks of age. The treated rats were about 1.5-fold more active in the nocturnal phase after administration of p-n-octylphenol than control rats. Immunohistochemical analyses revealed that p-n-octylphenol abolished immunoreactivity for tyrosine hydroxylase in the midbrain of 8 week-old rats, where terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling (TUNEL)-positive cells were also seen. Thus, this is the first demonstration that p-n-octylphenol certainly affected the developing brain, resulting in hyperactivity in the rat, most likely due to degeneration of mesencephalic tyrosine hydroxylase.
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