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(Stroke. 1999;30:662-668.)
© 1999 American Heart Association, Inc.

Original Contributions

Continuing Postischemic Neuronal Death in CA1

Influence of Ischemia Duration and Cytoprotective Doses of NBQX and SNX-111 in Rats

Presented at the Third International Workshop on Maturation Phenomenon in Cerebral Ischemia, Pozzilli, Italy, April 20–22, 1998, and published in abstract form (J Cereb Blood Flow Metab. 1995;15:S246).

Frederick Colbourne, PhD; Hui Li, MD Alastair M. Buchan, FRCP

From the Departments of Pathology (F.C.) and Clinical Neurosciences (H.L., A.M.B.), Alberta Stroke Program, Faculty of Medicine, University of Calgary, Alberta, Canada.

Correspondence to Dr Alastair M. Buchan, Alberta Stroke Program, Department of Clinical Neurosciences, Faculty of Medicine, Foothills Hospital, University of Calgary, 1403 29th St NW, Calgary, Alberta, Canada, T2N 2T9. E-mail buchan{at}ucalgary.ca

Background and Purpose—Transient forebrain ischemia results in a 24- to 72-hour delayed loss of CA1 neurons. Previous work has not assessed whether insult durations can vary the degree and maturation rate of CA1 injury and whether there are different ultrastructural features of death after brief or severe ischemia. We also tested whether known cytoprotective drugs achieve permanent or transient neuroprotection.

Methods—In the first experiment, ischemia was induced for 5, 15, or 30 minutes with the use of the 4-vessel occlusion rat model with 1- to 28-day survival. Others subjected to 5 or 15 minutes of ischemia and allowed to survive for 14 or 7 days, respectively, were examined with electron microscopy. Finally, we determined whether NBQX (30 mg/kg x3 at 0 or 6 hours after ischemia), an AMPA antagonist, and SNX-111 (5 mg/kg at 6 hours after ischemia), an N-type Ca²⁺ channel antagonist, provided enduring CA1 protection against 10 minutes of ischemia.

Results—CA1 damage was not detected at 24 hours. Thirty minutes of ischemia produced 47% and 84% CA1 damage at 2 and 3 days, respectively. A 15-minute occlusion yielded 11%, 74%, and 86% loss at 2, 3, and 7 days, respectively. Five minutes of ischemia produced an even slower progression with 24%, 52%, and 59% loss at 3, 7, and 14 days, respectively. Ultrastructural examination after 5 and 15 minutes of ischemia revealed necrosis with no morphological evidence of apoptosis. Both NBQX (P<0.021) and SNX-111 (P<0.001) significantly reduced CA1 death at 7 days (35%) but not at 28 days (80%) compared with saline treatment (79%).

Conclusions—Brief forebrain ischemia results in a slower progression of CA1 loss than more severe insults. Nonetheless, neuronal injury had necrotic, not apoptotic, morphology. NBQX and SNX-111 only postponed CA1 injury.

Editorial Comment

Influence of Ischemia Duration and Cytoprotective Doses of NBQX and SNX-111 in Rats

Presented at the Third International Workshop on Maturation Phenomenon in Cerebral Ischemia, Pozzilli, Italy, April 20–22, 1998, and published in abstract form (J Cereb Blood Flow Metab. 1995;15:S246).

James A. Clemens, PhD, Guest Editor

Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Ind

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