title: Threshold of calcium disturbances after focal cerebral ischemia in rats. Implications of the window of therapeutic opportunity.
abstract: OBJECTIVE
  One explanation for inconclusive results with calcium channel blockers in human acute stroke trials may be incomplete information about the time course of calcium-mediated ischemic neuronal injury. This study explores the temporal relation between duration of focal ischemia and the functional activity of increased intracellular calcium as measured by calcium-calmodulin binding.
  
  
  METHODS
  Calcium-calmodulin binding, determined by immunohistochemical assay of free calmodulin, was measured in 60 male spontaneously hypertensive rats after 2 minutes and after 1, 2, 4, and 24 hours of permanent tandem common carotid and middle cerebral artery occlusion, and after 1 and 2 hours of reversible middle cerebral artery occlusion followed by 1 and 22 hours of reperfusion, respectively. Light microscopic histological damage was measured after 1 hour of occlusion with 23 hours of reperfusion and after 24 hours of occlusion.
  
  
  RESULTS
  Significant loss of calmodulin staining in the core of the infarction was noted by 1 hour and became maximal after 4 hours of ischemia. No reversal of calmodulin staining loss was noted after reperfusion following 1 and 2 hours of ischemia. Cortical necrosis seen by light microscopy correlated well with the area of maximal calcium-calmodulin binding. The border zone area, represented by a mild loss of calmodulin staining surrounding the central core of maximal binding, gradually decreased in size and became incorporated into the central core after 4 hours of ischemia; it may represent an area of reversible ischemia.
  
  
  CONCLUSIONS
  Calcium-calmodulin binding correlates with duration of focal ischemia, and histological neuronal necrosis corresponds to the cortical areas displaying a significant loss of calmodulin staining. Inasmuch as loss of calmodulin staining represents a marker for calcium-mediated activity after ischemia, it suggests a window of opportunity within 4 hours after acute stroke for therapeutic intervention with calcium antagonists.
authors.affiliation: Department of Neurology, University of Texas Medical School, Houston 77030.
authors.forename: T J
authors.initials: TJ
authors.lastname: DeGraba
authors.forename: P T
authors.initials: PT
authors.lastname: Ostrow
authors.forename: J C
authors.initials: JC
authors.lastname: Grotta
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002545:Brain Ischemia / Q000378:metabolism* / Q000628:therapy; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D002544:Cerebral Infarction / Q000378:metabolism; D004056:Differential Threshold; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D051381:Rats; D011918:Rats, Inbred SHR; D015424:Reperfusion; D013194:Staining and Labeling
chemical_list: D002147:Calmodulin; D002118:Calcium