Stimulation of N-methyl-D-aspartate receptors induces apoptosis in rat brain.
To evaluate the contribution of apoptotic mechanisms to excitotoxin-induced neurodegeneration as well as to characterize the glutamate receptor subtypes involved, biochemical and morphological effects of intrastriatally administered NMDA receptor agonist N-methyl-D-aspartate (NMDA) or quinolinic acid (QA) were studied. Receptor autoradiography showed that NMDA (75-300 nmol) caused a loss of 18-68% of striatal D1 dopamine (DA) and 10-43% of NMDA receptors 7 days after drug administration. Treatment with QA (60-240 nmol) also led to a loss of 60-73% of D1 DA and 37-44% of NMDA receptors in the ipsilateral striatum. Agarose gel electrophoresis revealed that both NMDA and QA induced internucleosomal DNA fragmentation in the striatum 12 to 48 h after drug administration. NMDA- and QA-induced internucleosomal DNA fragmentation was attenuated by the protein synthesis inhibitor cycloheximide in a dose-dependent manner. Terminal transferase-mediated deoxyuridine triphosphate (d-UTP)-digoxigenin nick end labeling (TUNEL)-positive nuclei were found in the ipsilateral striatum in response to NMDA or QA treatment. In addition, many fragmented nuclei were observed in the NMDA or QA-treated striatum and propidium iodide staining showed profound nuclear condensation in the NMDA or QA-treated striatum. NMDA- and QA-induced internucleosomal DNA fragmentation and TUNEL-positive nuclei as well as nuclear condensation were abolished by the NMDA receptor antagonist MK-801, but not by the AMPA/KA receptor antagonist NBQX. MK-801, but not NBQX, also prevented NMDA or QA-induced striatal cell death. These results suggest that apoptotic mechanisms are involved in excitotoxin-induced striatal cell death. The initiation of an apoptotic cascade by NMDA or QA appears to be mediated by stimulation of NMDA but not AMPA/KA receptors.
Qin
Z H
ZH
Experimental Therapeutics Branch, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD 20892, USA.
Wang
Y
Y
Chase
T N
TN
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001345:Autoradiography; D053938:DNA Fragmentation; D004253:DNA Nucleotidylexotransferase / Q000378:metabolism; D003856:Deoxyuracil Nucleotides / Q000737:chemistry; D016291:Dizocilpine Maleate / Q000494:pharmacology*; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D005821:Genetic Techniques; D008297:Male; D009693:Nucleic Acid Hybridization; D011810:Quinoxalines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists*; D013268:Stimulation, Chemical
D003856:Deoxyuracil Nucleotides; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; D016194:Receptors, N-Methyl-D-Aspartate; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D016291:Dizocilpine Maleate; D004253:DNA Nucleotidylexotransferase