Morphological Analysis of Short and Long Term Changes after Ligation of Unilateral Common Carotid Artery in Gerbils

ABSTRACT

BACKGROUND: The ligation of the unilateral common carotid artery (CCA) in the gerbil has been known as an ischemic animal model showing various changes including selective neuronal necrosis as well as infarction. This study was performed to analyze the short and long term morphological changes of transient unilateral forebrain ischemia with special attention to astroglial proliferation. METHODS: 67 mongolian gerbils were subjected to 2 hr, 3 hr, 4 hr, or 5 hr of forebrain ischemia by the unilateral CCA ligation method. Each of the ischemic groups were examined after a 1 day, 3 day, or 7 day period of reperfusion. Long term reperfusion groups consisted of 2, 3, and 4 weeks of reperfusion after 5hr of unilateral CCA ligation. Morphological changes were analyzed by H-E staining and an immunohistochemical reaction with GFAP antibody. RESULTS: The ligation of the unilateral CCA, induced unilateral hemispheric infarction in 14 gerbils, selective neuronal necrosis (SNN) involving caudate in 1 gerbil, and delayed neuronal necrosis (DND) of the hippocampal CA1 neurons in 2 gerbils. Infarction was most frequent in 1 day reperfusion groups and did not show any differences according to the duration of ischemia. The GFAP reaction was strongly positive in the center of infarction at a 1 day period and negative at a 3 & 7 day period. The surrounding brain parenchyme progressively revealed increased positive reactions. Gerbils with SNN and DND showed moderately or markedly increased GFAP positive reactions in the unilateral caudate, thalamus, and hippocampus, whereas no apparent changes were shown by a H-E stain. CONCLUSIONS: Reactive astrogliosis is a stereotyped reaction of ischemic brain injury and is a more sensitive parameter than neuronal changes.