The four-vessel occlusion rat model: method for complete occlusion of vertebral arteries and control of collateral circulation.

Four-vessel occlusion in rats was introduced approximately 10 years ago to provide a rodent model of reversible forebrain ischemia. The model presented several advantages, which included ease of preparation, a high rate of predictable ischemic neuronal damage, a low incidence of seizures, and the absence of anesthesia. However, two issues concerning the efficient use of the four-vessel occlusion rat model as originally described by us'require clarification. First, several groupshave reported difficulty assuring complete occlusion of the vertebral arteries by electrocauterization through the alar foramina of the first cervical vertebra. Because this difficulty may stem partly from our failure to have adequately described details of this method in our original article, the following is provided to facilitate more effective use of the model. It is important to position the anesthetized rat's head in stereotactic ear bars with the head tilted down at approximately 30° to the horizontal. The cervical spine is gently stretched by placing tension on the rat's tail with a rubber band anchored to the table. These steps stabilize and rotate the first cervical vertebra such that the alar wings are horizontal to the table; the full perimeters of the alar foramina can therefore be seen. The alar foramina (see Figure 1 in Reference 1) are easily approached via a midline dorsal neck incision. A pivoting, dissection microscope with through-the-lens or direct lighting is essential to carry out the following procedure. Once the alar foramina are visualized with the microscope, a small (<1 mm) electrocautery needle is inserted vertically through the alar foramina and down into the bony tunnel of the first vertebra, through which the vertebral arteries travel. Brief, intermittent application of current to the needle tip will cauterize the vertebral arteries and avert bleeding in the majority of rats. In those rats