title: Excitatory amino acid regulation of the enkephalin phenotype in mouse embryonic spinal cord cultures.
abstract: Expression of the preproenkephalin gene in developing spinal cord-dorsal root ganglia (SC-DRG) cultures was determined by Northern analysis following treatments with different agonists and antagonists of the glutamate receptor. Cultures (10-12 days old) were treated with various concentrations (10(-7)-10(-3) M) of N-methyl-D-aspartate (NMDA), quisqualate, kainic acid (KA), 2-amino-5-phosphonovaleric acid (APV) and 5-methyl-10,11-dihydro-5H-dibenzo[a, d]cyclohepten-5,10-imine maleate (MK801) either with or without blocking spontaneous electrical activity with 1 microM tetrodotoxin (TTX). In electrically active cultures, treatments with NMDA and KA increased preproenkephalin transcripts (mRNAppENK), showing maximum effects at 1 microM (4-fold and 2-fold, respectively), while treatments with quisqualate and MK801 caused concentration-dependent down-regulation in mRNAppENK. The most effective concentrations of NMDA (1 microM) and quisqualate (10 microM) altered mRNAppENK levels within 4 h of treatment and peaked after 24 h for NMDA and 48 h for quisqualate treatment. Co-treatment with APV completely blocked the NMDA-induced rise of mRNAppENK. During electrical blockade, none of the concentrations of NMDA tested showed any effect on enkephalin expression, neither could NMDA pre-treatment prevent the TTX-induced down-regulation of mRNAppENK. Our results indicate that the activity-dependent establishment of the enkephalin phenotype is modulated through the selective activation of the NMDA-glutamate receptor.
authors.affiliation: Laboratory of Developmental Neurobiology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892.
authors.forename: R W
authors.initials: RW
authors.lastname: Summers
authors.forename: X R
authors.initials: XR
authors.lastname: Wu
authors.forename: S C
authors.initials: SC
authors.lastname: Fitzgerald
authors.forename: D E
authors.initials: DE
authors.lastname: Brenneman
authors.forename: D
authors.initials: D
authors.lastname: von Agoston
mesh_terms: D000596:Amino Acids / Q000502:physiology*; D000818:Animals; D015152:Blotting, Northern; D002478:Cells, Cultured; D015536:Down-Regulation / Q000187:drug effects; D004558:Electric Stimulation; D004745:Enkephalins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects; D008024:Ligands; D051379:Mice; D008810:Mice, Inbred C57BL; D016202:N-Methylaspartate / Q000037:antagonists & inhibitors / Q000494:pharmacology; D010641:Phenotype; D011247:Pregnancy; D011498:Protein Precursors / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism; D017470:Receptors, Glutamate / Q000187:drug effects / Q000378:metabolism; D013116:Spinal Cord / Q000196:embryology / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D004745:Enkephalins; D008024:Ligands; D011498:Protein Precursors; D012333:RNA, Messenger; D017470:Receptors, Glutamate; D013779:Tetrodotoxin; D016202:N-Methylaspartate; C033660:preproenkephalin