Characteristics of circle of Willis variations in the mongolian gerbil and a newly established ischemia-prone gerbil group.

Mongolian gerbils (Meriones unguiculatus) have an incomplete circle of Willis (CoW), as a result of which approximately 30-40% of these animals develop focal cerebral ischemia after unilateral carotid occlusion (UCO). There are four types of patterns of the anterior and posterior communicating arteries (ACoAs and PCoAs, respectively) of the CoW and they determine the severity of the ischemic symptoms. We used 398 gerbils from five generations, including a selectively bred ischemia-prone group, to investigate post-UCO ischemic symptoms and possible correlations of ACoA and PCoA patterns between parents and their progeny. We observed that if the parents had complete ACoAs, their progeny also had complete ACoAs, and we found significant differences when the parents' ACoAs were incomplete: in 60.4% of offspring the type of ACoA was consistent with that of the mother and in 48.2% it was consistent with that of the father. The severity of the neurological symptoms after UCO was significantly related to the patterns of the ACoAs when PCoAs were absent. The proportion of UCO ischemia in gerbils with incomplete ACoAs was significantly higher than in those with complete ACoAs. After selectively breeding five generations, the proportion of UCO ischemia increased from 40% in the F1 animals to 75% in the F5 animals. Our results suggest that variations in the CoW are genetic and demonstrate that we successfully established an ischemia-prone group of gerbils.