Largest Rodent Could Be Lab Rat for Stroke Studies People undergo dramatic changes during puberty, but we've got nothing on the capybara. For reasons still mysterious to scientists, the world's largest rodent shuts off one of the main supplies of blood to its brain when it reaches sexual maturity. That makes the South American rodent an ideal natural model for studying stroke, a group of researchers in Brazil now proposes.
In both humans and capybaras, there are two main sources of blood to the brain: the internal carotid artery, which runs up each side of the neck, and the basilar artery, which begins at the base of the skull. When a capybara begins to sexually mature at about 6 months of age, its internal carotid artery becomes clogged with collagen and can no longer transmit blood. Still, "capybaras seem to cope very well" with the transformation, says University of São Paulo veterinary anatomist and surgeon Augusto Coppi. As the carotid artery closes, the rodent's basilar artery doubles in size to keep the brain supplied with blood.
When one of these arteries becomes blocked in a human, however, the other "doesn't have enough time to adapt," Coppi says—and the result is a stroke. In a recent paper in Cells Tissues Organs, he and colleagues argue that studying the capybara could help scientists figure out how to make human arteries behave more like their capybara counterparts and quickly pick up the slack if their companion shuts down.