Involvement of N-methyl-D-aspartate receptors in post-hypoxic depression of the dorsomedial medulla in cats.
Pressor and sympathoexcitatory responses induced by microinjection of glutamate (Glu) into the dorsomedial medulla (DM) were depressed after hypoxia in anesthetized cats. This study was undertaken to investigate which Glu receptor subtypes would be involved in the post-hypoxic depression. Hypoxia was induced by inhalation of a 5% O(2) and 95% N(2) gas mixture. The pressor and sympathoexcitatory responses to microinjections of N-methyl-D-aspartic acid (NMDA) or alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) into the DM were significantly depressed after hypoxia, suggesting the involvement of both NMDA and AMPA receptors. However, pretreatment with kynurenic acid or DL-2-amino-5-phosphonopentanoic acid, but not 6-cyano-7-nitroquinoxaline-2,3-dione, 5 min before hypoxia could effectively prevent the post-hypoxic depression of Glu-induced responses. These results further suggest that post-hypoxic depression of Glu-induced responses in the DM was predominately mediated by NMDA receptors.
Hong
Ling-Zong
LZ
Department of Education and Research, Taichung Veterans General Hospital, 160, Sec. 3 Taichung Kang Rd., Taichung 40705, Taiwan, ROC. lzhong@vghtc.vghtc.gov.tw
Chai
Chok-Yung
CY
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D003864:Depression, Chemical; D004305:Dose-Response Relationship, Drug; D018690:Excitatory Amino Acid Agonists / Q000008:administration & dosage / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D000860:Hypoxia / Q000503:physiopathology*; D007736:Kynurenic Acid / Q000494:pharmacology; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D008845:Microinjections; D016202:N-Methylaspartate / Q000008:administration & dosage / Q000494:pharmacology; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*; D013127:Spinal Nerves / Q000187:drug effects; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000008:administration & dosage / Q000494:pharmacology
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D016202:N-Methylaspartate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D007736:Kynurenic Acid