The antioxidant melatonin reduces cortical neuronal death after intrastriatal injection of kainate in the rat |
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Authors: | S T Chen J I Chuang |
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Affiliation: | (1) Department of Anatomy, College of Medicine, National Cheng Kung University, Tainan, Taiwan, Republic of China, TW;(2) Department of Physiology, College of Medicine, National Cheng Kung University, Tainan, Taiwan, Republic of China e-mail: jichuang@mail.ncku.edu.tw Tel.: 886-6-2353535 ext. 5460, Fax: 886-6-2362780, TW |
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Abstract: | The anti-excitotoxic efficacy of the pineal hormone melatonin was investigated in kainate-injured brains of rats. Kainate
(a glutamate-receptor agonist, 2.5 nmol in 1 μl) was directly injected to unilateral striatum. Melatonin (10 mg/kg) was administrated
intraperitoneally 1 h before and 1, 3, and 5 h after intrastriatal kainate injection in adult Sprague-Dawley rats. Three days
after kainate injection, a significant neuronal damage was found, as determined by Nissl staining and the TUNEL method, not
only in the injected striatum, but also in the ipsilateral neighboring cortex. The kainate-induced cortical apoptotic neuronal
death was significantly attenuated by treatment with melatonin compared with the vehicle control group. However, no detectable
changes were observed in the contralateral side of the brain in either vehicle- or melatonin-treated rats. Moreover, the biochemical
results indicated that kainate can indeed induce oxidative stress, such as a decrease in the content of total glutathione
(GSH), oxidized glutathione (GSSG), and an increase in the ratio of GSSG/GSH in the striatum and cortex compared with the
contralateral brain regions. In the kainate-injected striatum, melatonin did not reduce the oxidative stress, but in the neighborhood
of injected area-cortex, kainate-induced oxidative stress was significantly reduced by melatonin. Enhancement of glutathione-peroxidase
activity was induced by intrastriatal kainate injection, not only in the cortical area of control and melatonin-treated rats,
but also in striatum of control rats. However, a large elevation was found in the melatonin-treated cortex. Taking the morphological
and biochemical data together, the present results suggest that melatonin functions as an antioxidant by upregulating the
glutathione antioxidative defense system, thereby reducing neuronal death caused by excitotoxicity and preventing the kainate-induced
damage from spreading to adjacent brain regions.
Received: 16 December 1997 / Accepted: 30 July 1998 |
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Keywords: | Melatonin Kainate Glutathione Apoptosis Excitotoxicity |
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