A REPRODUCIBLE MODEL OF MIDDLE CEREBRAL INFARCTS, COMPATIBLE WITH LONG-TERM SURVIVAL, IN AGED RATS

Background and Purpose Stroke is a disease associated with aging, but experimental stroke studies are generally done in young male animals. Because there are numerous differences associated with aging, such as an altered immune system and altered neurochemistry, that could affect the outcome of these experiments, a model of reproducible cerebral infarction in aged rats is needed. Methods We attempted to produce middle cerebral artery (MCA) infarcts in aged (22 months of age) rats using two standard methods. A nylon suture with a heat-induced bulb was passed through the external carotid artery in seven animals, with an attempt to place the tip at the origin of the MCA. The MCA was ligated through a craniotomy just proximal to the internal cerebral vein in 14 rats. Survival potential was tested by attempting 2-week survival in four rats and 2-month survival in one rat. Results The suture model failed to produce MCA infarcts, even when the bulb of the suture was properly placed in the MCA. The intracranial MCA occlusion resulted in reproducible MCA infarcts. There were no deaths, including the animals allowed to survive 2 weeks and 2 months. Conclusions We conclude that reproducible MCA infarcts can be produced in aged rats by craniotomy and that these lesions may be compatible with long-term survival. This should be a useful technique for studying therapeutic interventions and rehabilitation strategies in an animal model that immunologically and neurochemically more closely resembles humans at risk for stroke.