Consistent injury in the striatum of C57BL/6 mice after transient bilateral common carotid artery occlusion

The recent availability of transgenic mice enables us to study the functional role of single gene products in cerebral ischemia. To establish an experimental murine model of transient forebrain ischemia, this study examined the temporal profile of ischemic neuronal damage in the striatum after bilateral common carotid artery occlusion.

C57BL/6 mice, which are frequently used for genetic manipulations, were subjected to 15-minute bilateral common carotid artery occlusion. Ischemic injury was examined (4, 8, 24, 48, and 96 h after reperfusion) by Nissl staining, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end-labeling, and nuclear staining with Hoechst 33258 dye.

Regional cerebral blood flow was decreased to 11 +/- 6% of control values during the ischemic insult. Striatal injury was observed in 95% of animals examined after 15-minute bilateral common carotid artery occlusion. The number of small and medium-size neurons in the striatum was significantly (P < 0.05) decreased 8 hours after reperfusion and continued to decrease until 96 hours, whereas the number of large neurons remained constant. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end-labeling-positive cells appeared in the dorsomedial region of the striatum 48 hours after the ischemic insult and throughout the striatum 96 hours after the ischemic insult. Brain sections stained with Hoechst 33258 dye also demonstrated apoptotic nuclei 96 hours after the ischemic insult.

Striatal injury after transient forebrain ischemia is reproducible in C57BL/6 mice and is a good model to study the molecular mechanisms of ischemic injury, including delayed neuronal death, using transgenic mice.