title: Immediate and Long-Term Outcome of Acute H2S Intoxication Induced Coma in Unanesthetized Rats: Effects of Methylene Blue.
abstract: BACKGROUND
  Acute hydrogen sulfide (H2S) poisoning produces a coma, the outcome of which ranges from full recovery to severe neurological deficits. The aim of our study was to 1--describe the immediate and long-term neurological effects following H2S-induced coma in un-anesthetized rats, and 2--determine the potential benefit of methylene blue (MB), a compound we previously found to counteract acute sulfide cardiac toxicity.
  
  
  METHODS
  NaHS was administered IP in un-sedated rats to produce a coma (n = 34). One minute into coma, the rats received MB (4 mg/kg i.v.) or saline. The surviving rats were followed clinically and assigned to Morris water maze (MWM) and open field testing then sacrificed at day 7.
  
  
  RESULTS
  Sixty percent of the non-treated comatose rats died by pulseless electrical activity. Nine percent recovered with neurological deficits requiring euthanasia, their brain examination revealed major neuronal necrosis of the superficial and middle layers of the cerebral cortex and the posterior thalamus, with variable necrosis of the caudate putamen, but no lesions of the hippocampus or the cerebellum, in contrast to the typical distribution of post-ischemic lesions. The remaining animals displayed, on average, a significantly less effective search strategy than the control rats (n = 21) during MWM testing. Meanwhile, 75% of rats that received MB survived and could perform the MWM test (P<0.05 vs non-treated animals). The treated animals displayed a significantly higher occurrence of spatial search than the non-treated animals. However, a similar proportion of cortical necrosis was observed in both groups, with a milder clinical presentation following MB.
  
  
  CONCLUSIONS
  In conclusion, in rats surviving H2S induced coma, spatial search patterns were used less frequently than in control animals. A small percentage of rats presented necrotic neuronal lesions, which distribution differed from post-ischemic lesions. MB dramatically improved the immediate survival and spatial search strategy in the surviving rats.
authors.affiliation: Department of Medicine, Division of Pulmonary and Critical Care Medicine, Pennsylvania State University, College of Medicine, Hershey, PA, United States of America.
authors.forename: Takashi
authors.initials: T
authors.lastname: Sonobe
authors.affiliation: Department of Medicine, Division of Pulmonary and Critical Care Medicine, Pennsylvania State University, College of Medicine, Hershey, PA, United States of America.
authors.forename: Bruno
authors.initials: B
authors.lastname: Chenuel
authors.affiliation: Department of Comparative Medicine, Pennsylvania State University, College of Medicine, Hershey, PA, United States of America; Department of Pathology, Pennsylvania State University, College of Medicine, Hershey, PA, United States of America.
authors.forename: Timothy K
authors.initials: TK
authors.lastname: Cooper
authors.affiliation: Department of Medicine, Division of Pulmonary and Critical Care Medicine, Pennsylvania State University, College of Medicine, Hershey, PA, United States of America.
authors.forename: Philippe
authors.initials: P
authors.lastname: Haouzi
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D003128:Coma / Q000139:chemically induced* / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D006862:Hydrogen Sulfide / Q000506:poisoning*; D008297:Male; D008751:Methylene Blue / Q000494:pharmacology*; D009336:Necrosis; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D008751:Methylene Blue; D006862:Hydrogen Sulfide