Figure 2: Brief summary of animal models of CA used in recent experimental studies. A brief summary of animal models used in recent experiments is shown. The particularities, advantages, and disadvantages of each model are as follows. *1: Induced hypertension can be achieved by several methods such as the ligation of the renal artery, high salt diet intake, deoxycorticosterone treatment, and angiotensin II injection. *2: This model is mainly used for the development of endovascular devices and not for the analysis of the molecular mechanisms of CA formation. *3: The new bifurcation is created at the carotid artery by side-to-end ligation. This model is suitable for the analysis of hemodynamics-induced CAs, but the hemodynamic stress is greater than in the intracranial arteries where the CAs are formed. *4: CAs can be induced with a high frequency and with a low risk, but they seldom rupture. BAPN treatment enlarges the size of the induced CAs. *5: BAPN intake or local elastase injection is essential for the induction of CAs. Lipopolysaccharide can also enhance CA formation and huge CAs can sometimes be observed. *6: It takes over 1 year to induce CAs, but their incidence is high. *7: It is necessary to perform bilateral oophorectomy to effectively induce CAs. *8: Large CAs are frequently induced in the posterior circulation. This model has the potential to be used in studies linking hemodynamics and molecular expression. *9: Bilateral CCA ligation results in high mortality, but can induce large CAs in the posterior circulation. CCA: common carotid artery.