Brain Vasculature in the Mongolian Gerbil

A unique blood supply to the brain, the “Circle of Willis” (COW), exists in all mammals except for the Mongolian gerbil (Meriones unguiculatus). The posterior connection between the basilar artery and the carotid artery system has been found to be missing in most gerbils. Furthermore, in some of the animals, the anterior communication was not complete, thus leading to partial ischemia following unilateral carotid artery occlusion. Due to those peculiar characteristics, the Mongolian gerbil today has become a widespread animal model for cerebral ischemia studies. M. unguiculatus has been used in most of the studies, while the level of ischemia has been evaluated by the development of neurological symptoms created by the occlusion of the carotid arteries. In this study, we investigated the vasculature structure of the commonly used gerbil, M. unguiculatus (MU-TF), and compared it to the vasculature of the Israeli gerbil, Meriones tristrami, as well as to that of the Albino rat. We determined the correlation between the anatomical pattern of the blood vessels and the biochemical responses during partial or complete ischemia and anoxia by monitoring the oxidation-reduction state of the intramitochondrial NADH using an in vivo surface fluorescence technique. The corrected fluorescence signal was found to be inversely correlated with oxygen availability. This is the first time that the brain vasculature of two lines of M. tristrami (MT-HU, MT-BD) has been investigated. Gerbils belonging to Meriones unguiculatus obtained from Tumblebrook Farms and from the NY Institute for Basic Research were compared to two lines of Meriones tristrami obtained from two different breeders in Israel. In all groups of gerbils and in the albino rats, a significant correlation was found between the anatomical patterns of the Circle of Willis and the metabolic responses to ischemia as evaluated by NADH redox state measurements, namely, that with a complete anterior anatomical Circle of Willis, the metabolic response to unilateral occlusion was minimal.