title: Transcriptional responses of the nerve agent-sensitive brain regions amygdala, hippocampus, piriform cortex, septum, and thalamus following exposure to the organophosphonate anticholinesterase sarin.
abstract: BACKGROUND
  Although the acute toxicity of organophosphorus nerve agents is known to result from acetylcholinesterase inhibition, the molecular mechanisms involved in the development of neuropathology following nerve agent-induced seizure are not well understood. To help determine these pathways, we previously used microarray analysis to identify gene expression changes in the rat piriform cortex, a region of the rat brain sensitive to nerve agent exposure, over a 24-h time period following sarin-induced seizure. We found significant differences in gene expression profiles and identified secondary responses that potentially lead to brain injury and cell death. To advance our understanding of the molecular mechanisms involved in sarin-induced toxicity, we analyzed gene expression changes in four other areas of the rat brain known to be affected by nerve agent-induced seizure (amygdala, hippocampus, septum, and thalamus).
  
  
  METHODS
  We compared the transcriptional response of these four brain regions to sarin-induced seizure with the response previously characterized in the piriform cortex. In this study, rats were challenged with 1.0 × LD₅₀ sarin and subsequently treated with atropine sulfate, 2-pyridine aldoxime methylchloride, and diazepam. The four brain regions were collected at 0.25, 1, 3, 6, and 24 h after seizure onset, and total RNA was processed for microarray analysis.
  
  
  RESULTS
  Principal component analysis identified brain region and time following seizure onset as major sources of variability within the dataset. Analysis of variance identified genes significantly changed following sarin-induced seizure, and gene ontology analysis identified biological pathways, functions, and networks of genes significantly affected by sarin-induced seizure over the 24-h time course. Many of the molecular functions and pathways identified as being most significant across all of the brain regions were indicative of an inflammatory response. There were also a number of molecular responses that were unique for each brain region, with the thalamus having the most distinct response to nerve agent-induced seizure.
  
  
  CONCLUSIONS
  Identifying the molecular mechanisms involved in sarin-induced neurotoxicity in these sensitive brain regions will facilitate the development of novel therapeutics that can potentially provide broad-spectrum protection in five areas of the central nervous system known to be damaged by nerve agent-induced seizure.
authors.affiliation: Cell and Molecular Biology Branch, US Army Medical Research Institute of Chemical Defense (USAMRICD), 3100 Ricketts Point Road, Aberdeen Proving Ground, MD 21010-5400, USA.
authors.forename: Kimberly D
authors.initials: KD
authors.lastname: Spradling
authors.forename: Lucille A
authors.initials: LA
authors.lastname: Lumley
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Robison
authors.forename: James L
authors.initials: JL
authors.lastname: Meyerhoff
authors.forename: James F
authors.initials: JF
authors.lastname: Dillman
mesh_terms: D000679:Amygdala / Q000187:drug effects / Q000502:physiology; D000818:Animals; D000927:Anticonvulsants / Q000627:therapeutic use; D001285:Atropine / Q000627:therapeutic use; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology; D002619:Chemical Warfare Agents / Q000494:pharmacology; D002800:Cholinesterase Inhibitors / Q000494:pharmacology*; D003975:Diazepam / Q000627:therapeutic use; D020869:Gene Expression Profiling; D053263:Gene Regulatory Networks / Q000187:drug effects; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D008297:Male; D046228:Microarray Analysis; D018727:Muscarinic Antagonists / Q000627:therapeutic use; D010091:Oximes / Q000627:therapeutic use; D025341:Principal Component Analysis; D011725:Pyridines / Q000627:therapeutic use; D051381:Rats; D017207:Rats, Sprague-Dawley; D012524:Sarin / Q000494:pharmacology*; D012640:Seizures / Q000139:chemically induced / Q000188:drug therapy / Q000503:physiopathology; D020665:Septum of Brain / Q000187:drug effects / Q000502:physiology; D013788:Thalamus / Q000187:drug effects / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism
chemical_list: D000927:Anticonvulsants; D002619:Chemical Warfare Agents; D002800:Cholinesterase Inhibitors; D053583:Interleukin-1beta; D015850:Interleukin-6; D018727:Muscarinic Antagonists; D010091:Oximes; D011725:Pyridines; D014409:Tumor Necrosis Factor-alpha; D001285:Atropine; C060977:pyridine-2-aldoxime; D012524:Sarin; D003975:Diazepam